I would consider to move the Ctrl and Shift keys to the left. There are several moments when you have to use this keys in combinations with the coursor keys. And all keys on the right is not very easy to use.

And perhaps, if the Space Key is not in the middle on the bottom of the keyboard, why not make it as large as the other keys to have more space for some other useful keys. In my opinion at the N900 it would be also enought to use only the space of a single key for the Space Key and have a Button more for other stuff... At example my suggestion would be a Alt key and a second Shift?