After a public preview and some bug fixes, the three major Office programs are now available for some Android tablets.
Microsoft Word for Android, Excel for Android and PowerPoint for Android are now available from Google Play. There’s also an OneNote app already available.

If you’ve installed the preview/beta versions of the apps then they will be automatically updated to the final release, if that hasn’t happened already.
Most of the features in the Android apps are available to everyone.
An Office 365 subscription that includes Office software is needed to access to some advanced features or, as Microsoft puts it, ‘unlock the full Office experience’.
The trap
The catch with the Office for Android apps is the limitations on what devices can install them. This has been a problem throughout the testing period with regular complaints from would-be testers that the apps can’t be installed. This is from the Word for Android app info:

Screen Size
The main problem is screen size, which isn’t made clear by Microsoft with the important detail split between a bullet point and later paragraph.
Only Android devices with screens between 7″ and 10.1″ can install the Office for Android apps.
The 7″ minimum is different from the 8″ specification during the testing. It’s good news because the popular (and really nice) Nexus 7 device is now compatible with the Office apps.
The 10.1″ maximum is a real limit. We’ve seen reports that even a 10.2″ screen device won’t install the apps, certainly a 10.5″ device won’t work. We’re not sure if this upper limit has been done for technical reasons or to limit the appeal of larger tablets which are rivals for Windows laptops.
Android devices under 7″ can use the Microsoft Office Mobile app which has Word, Excel and PowerPoint bundled together.
Processor
If you thought having an Intel based Android devices would make it more likely to get Microsoft Office then you’re in for a rude shock. NO Android devices using Intel made CPU’s will accept Office for Android apps.
Happily, most Android devices use ARM based processors so most people won’t have this problem.
KitKat only
At this stage Office for Android only works with Android ‘KitKat’ v4.4.x not the more recent Lollipop v.5.x OS nor older JellyBean.
If you’re buying a new Android tablet, make sure it does NOT have the latest ‘Lollipop’ already installed. The latest Google Nexus devices have Lollipop which is marketed as a good feature, but for Office users it isn’t (for the moment).
Inevitably the Office apps will be upgraded to include Lollipop compatibility, the question is … when?
The 1GB RAM limit (not the storage) should not be a problem for most devices with a larger screen size.
How to tell?
You can find out if your Android device is compatible simply by trying to download the apps from the Google Play store. Google Play will only let you install compatible applications and there’s no harm in trying.
The big annoyance is that there’s no way to tell why your device isn’t compatible with an Android app. It could be the screen size, CPU, operating system or some other reason but there’s no way to tell. This is a Google Play limitation.

As you can see, any ineligible devices are grayed out with a short phrase ‘This item is not compatible with your device‘ but not detail of what the problem is.
If you’re buying an Android device, don’t rely on the promises of sales people. Try the device for yourself (which is a good idea anyway) and go to Google Play, find one of the Office for Android apps and ensure that the install button is available.