I'm playing with an ASUS Transformer tablet, which is interesting in that it has a hardware keyboard which can be unplugged. I thought I'll post a few things about how this works in practice, from the perspective of a keyboard addict. Not the kind of thing most reviews mention, nor indeed the kind of thing most people care about.
I'll try to avoid repeating things that the average review already mentions. Beware: this article is nit-picky.
The keys are fairly usable for touch typing, just large enough to be acceptable (my hands are average-sized). The arrow keys are too small for true comfort, but still better than 90% of modern laptops, which have halved their height.
There are no dedicated Page up/Page down/Home/End keys. I use these keys a lot, so this is a huge drawback. I have to press Fn+Arrow for these, which adds up for things like Ctrl+Shift+Home. Unfortunately, this isn't exactly unusual for laptop keyboards, but this also means you might already know what this feels like, and hence whether this is a problem for you personally.
There are no keys for Delete or Insert at all. Insert has certainly fallen into disuse lately – in no small part due to how most UIs that use it for insert/overwrite mode utterly fail in making it obvious that you can switch modes by pressing Insert, or especially how to change it back if you've pressed Insert by accident. But omitting Delete is absolutely unforgivable.
There are no F-keys, but I found this to be no big deal. All the applications are new and none rely on F-keys. I couldn't possibly tolerate that on a Windows machine, but it's fine on Android. What you get in return is a bunch of dedicated keys for things like volume, brightness and such, which is really rather convenient.
The Escape key has been re-branded as the "return" key. It works pretty intuitively; it feels just like using Escape on Windows PCs.
It's basically impossible to type if you leave the touch pad enabled. Every time you press Space, you also tap the mouse. There is a dedicated key to turn the touch pad on/off, but having to turn it on/off constantly is a huge pain.
Alt+Tab sort of works. There are two issues with Alt+Tab. Firstly, the only Alt on the hardware keyboard is the right Alt. Secondly, pressing Alt+Tab once doesn't switch applications; it just shows the switch UI with the current application selected. To switch between two apps, get ready to Alt+Tab+Tab. Alt+Shift+Tab works similarly.
The Search key (located where the left Alt would be found on traditional keyboards) doesn't do anything in most applications. Quite a wasted opportunity in my opinion. Plus, I see no reason why Search+Tab couldn't double up as Alt+Tab.
Tab generally works to focus the next UI control. Enter often does the same as Tab in various built-in dialogs. Arrow keys also generally work for changing UI focus, even in third-party apps.
Alt+shortcuts are non-existent on Android. Prepare to either use Tab a lot, or to touch the controls you need.
Ctrl+C, Ctrl+V and Ctrl+X work everywhere I tried them, which is great. As already mentioned, there is no Insert or Delete key, so forget about Ctrl+Ins, Shift+Ins and Shift+Del.
Ctrl+Arrows usually work to jump a word at a time. Ctrl+Shift+Arrows has an extremely annoying OS-wide bug: if you press Ctrl, then Shift, then Arrow, you will get the same as Ctrl+Arrow. If you want to select by words, you had better press Shift, Ctrl, Arrow. Needless to say, this means that you cannot Ctrl+Arrow to the desired position, add Shift, and select by words from there. Plus, if you simply Ctrl+Shift+Arrow without thinking, 50% of the time you'll have pressed them in the wrong order. In other words, FAIL.
Ctrl+L works in Chrome to focus the URL bar, which is certainly nice. Ctrl+R doesn't reload the page, and there is no F5 of course. Ctrl+K (focus URL bar in search mode) doesn't do anything. I forgot to test Ctrl+T or Ctrl+click, and I no longer have the device available.
Arrows didn't work in some drop-downs, like the YouTube app's search auto-completion list.
Incredibly, the YouTube app's search box is entirely incompatible with the physical keyboard. Trying to type in that box focuses the list of recommended videos instead. Coupled with the fact that you can't show the on-screen keyboard while the physical one is connected, you basically can't search in the YouTube app without undocking the physical keyboard. This is aggravated by the fact that the video stops and loses position whenever the dock is connected and disconnected. All in all, the YouTube app is probably the worst experience I've had on this ASUS device.
It's possible to switch keyboard layouts. Ctrl+Shift opens up the layout selection dialog, but it appears to require touch to actually change languages, making it a bit awkward if you switch a lot. I did not find a single key combination that just switches to the next layout, or selects a specific layout.
I've tested the device with the Russian layout. Curiously enough, while it works in most places, the Chrome URL bar doesn't support typing in Russian. Even with the Russian layout selected, the physical keys produce English letters. This is a significant problem, because the Chrome URL bar doubles as the search box. In order to google something in Russian, I first have to navigate to google.com, and then type my query into the website.
I didn't test this, but I suspect the same also applies to other non-Latin scripts.
The hardware keyboard works properly only if you have the ASUS keyboard selected. I didn't like it very much for on-screen typing (with the keyboard undocked). If you want to use a different on-screen keyboard, be prepared to switch every time you dock/undock the physical keyboard.
The ASUS on-screen keyboard has a key whose only purpose is to show/hide another key: the language selection key. This makes very little sense, of course: you could just always show the language selection key instead of this special weird key, thus using the same amount of screen space.
When typing in the URL bar, the ASUS keyboard adds a bunch of keys either side of Space, making Space the same width as every other key. This is problematic because, as already mentioned, Chrome uses the URL bar for entering google queries, which tend to contain spaces.
There are a few other usability things not related to the keyboard that I'd like to mention.
Small fonts are ubiquitous. This device doesn't have a particularly high-DPI screen. It also doesn't offer sub-pixel anti-aliasing. Result: very unreadable text in lots of places. The Chrome's tab labels, for example. They're terrible. There doesn't even appear to be much hinting in the font used, rendering the horizontal bar of the "e" character perfectly smeared across two rows of pixels. Having said that, some small fonts look a lot better (especially bold ones), and the problem is essentially unnoticeable on larger fonts.
If you have more than one app associated with an action, a dialog shows, asking which one you'd like to use. If you don't want to set a permanent association and be prompted every time, you have to tap twice. First select the app, then "Just once". A single tap would have worked much better. Plus, if you have accidentally selected "Always", or want to change your choice, you can only erase every association at once, among with a bunch of other settings.
The same applies to switching Wi-Fi networks. You have to tap twice, plus if you're not careful, your second tap might delete the network instead. I'd prefer a single tap to switch, or tap-and-hold for extra options like "forget".
It's not possible to drag an app from the desktop directly into the "Uninstall" bin. You have to find the app in the list of all apps, and uninstall from there.
If you're an AdBlock convert, you can block some ads without rooting the device. There is no DOM-based AdBlock for Chrome. I haven't used Firefox much on this device because it was very laggy (frankly, not unlike the desktop Firefox; it just shows a lot more on the much slower Android device).
Can this device...
... replace my laptop?
Hell no. But then, I could have said that without even trying any of the above things. My laptop must be able to run Visual Studio and FAR. This immediately eliminates every non-Windows non-Intel device from the list of candidates.
... be useful to occupy a child?
Absolutely. Totally. Perfect match for 1 year olds and older. Just make sure you sign out of Skype first...
... be useful to me alongside my laptop?
Unlikely. I really can't see what I would prefer to do on this device when I have the laptop. I can't see taking this device with me on a trip instead of the laptop just because it's a little lighter. Of course an Android phone is a different story altogether.
Given a desktop, a laptop and an Android phone, there really is no space left for a device the size of a laptop but the feature-set of a phone. It's best for people who don't feel they need a computer at all, and just want a larger smartphone-like device.