Like bikes and steaks, thickness is relative to the benefits it brings. The N900 fits in my pockets and for me it feels more or less in the same league as the very popular phones I have been using since I joined Nokia (5200, N95, N81, N82, E71). Also as a user of the three Internet Tablets I'm just amazed about the size reduction increasing the features and keeping the same type of user experience.

I'm not an engineer and I don't even know exactly what are the layers that bring that thickness but with a high density display, hardware keyboard, stereo speakers, 5Mp camera and a build quality that passes the Nokia drop tests I actually feel our hardware designers and engineers did a great job (again).

PS: also think about all the people that usually don't carry the phone in their pockets e.g. most women and there is plenty of them.