Imo for a smartphone it is too thick and too heavy. For an internet tablet, weight and thickness would be ok.

Of course on the other hand the screen seems to be approprately sized for a smarphone, but too small for an internet tables.

Apparently Nokia couldn't decide whether the N900 shall be a smartphone or an internet tablet, so they made it a little bit of both.

Which is the reason, why I definitely won't buy it, but wait instead for the next meamo devices. Hopefully these will either omit the keyboard and be much more lightweight and thinner to be a usable smartphone. Or add a reasonably sized screen to be an internet tablet.
Both would be ok for me - for different usecases.