Rover runs on MAEMO, which is a linux flavoured OS. It is successor to Nokia’s tablets N800 & N810. The best thing about N900 Rover is that it has a sim slot, so you can double it up as phone. However, I doubt how many users will find it fashionable to use a huge piece of bar near their earpiece.
Rover also sports a 5 MP camera with Car Zeiss lens, has a TV output, a 3.5mm headphone jack and a massive 3.5-inch WVGA screen.
From the pictures, the keyboard looks like that of adopted from Nokia N97. With Rover, Nokia seems to be in spits on whom to target- the netbooks or smartphones users. Well it will be clear whether they are successful with the experiment when Nokia launches Nokia N900 Rover soon.