I thought thin devices looked cool, but in your hand too thin is difficult to grip. Sometimes a little bit of girth adds to the gripping comfort. It just sits very naturally in the palm instead of having to hold with the fingers. My N95 made me realise this.
So I wouldnt mind a little bit of thickness as long as its not a brick.
The thickness slightly worries me too, but I'd have to see a device in the flesh to be sure. Ideally I'd like to see if it fits ok in jeans pockets while sat down, but I'm not too sure the mobile phone shop would be happy with that!
Maybe I should find or make something the same size and try it...
Did you know a RAZR is as thick as an n810? I was shocked. So, now imagine an iPhone that is 4mm thicker than a RAZR. That's the n900. I'm one of those who wishes there wasn't a physical keyboard, so further imagine that my kind of n900 could be as thin as a RAZR. That would be cool.
Obviously getting thinner and lighter is always the objective, but there are always some trade-offs (w/ having keyboard, user-replacable battery etc.).
The N900 is some 50g+ heavier than the iphones (133/135g) so one of next year's Maemo Nokia's (possibly without physical keyboard) might be expected to be thinner and lighter than those two, while still offering more features.
As a tablet guy I'd also welcome a thinner but especially a bit wider device, supposing there's a nice-sized edge-to-edge screen.
Only getting near 100g or below do I consider gadgets to be comfortably shirt-pocketable and it will be a while before phone-tablets with keyboard will get that light (or thin).
), any day.