I was reading at Engadget that the keyboard is supposed to completely suck on the Droid (according to more than one person). And someone else noted that the camera is less than stellar. I don't really know how the engineering on these things works, but I wonder if Motorola skimped on a lot of components. So on paper the Droid looks pretty comparable to the N900. But in practice cramming so much in a super thin space resulted in cutting a lot of corners.

I do agree the stylus is a bit of an odd choice.

I've also read that the N900 was conceived more as a development device than a consumer device, but then Nokia made a different decision about what to do with it. So Perhaps Nokia wasn't making it's biggest effort to engineer for thinness.

Also I believe the case on the Droid is made of metal. Perhaps that allows the material to be a little thinner, at least accounting for 1mm?