This limited range of supported formats is due to be addressed in a forthcoming (free) update to the iOS app.This will enable you to open files on the Kingston Wi-Drive using other apps on your iPhone, iPod touch or iPad (as the Seagate GoFlex Satellite already allows).
Importantly, this will also mean you can actually edit the files on the Wi-Drive, rather than just viewing them.
Another current limitation of the app is that it doesn't enable you to copy files from the drive to your device. Again, this will be added in the forthcoming update and will be a useful addition, meaning you can transfer things across to access locally if the Wi-Drive is running low on battery, or move a film onto your iPad before you get onto a flight, since you're not meant to use Wi-Fi in the air.
The update will also allow you to delete items on the Wi-Drive, which you currently have to do on a computer.
We'd also like to see some more attention paid to the app's performance and responsiveness, too. It currently feels a bit slow and cumbersome, and lacks the design panache we've come to expect of good iOS apps. For example, if you tap back out of a video mid-way through, it doesn't remember where you had got to when you next open it. Sigh.
Since the files remain within the Wi-Drive app, you can't integrate music on the drive with the playlists you've already got on your device, for example.
While this limitation is down to the way iOS works rather than the Wi-Drive itself, it still adds an unwelcome layer of complication to getting at your stuff.