I think the N950 is the perfect phone. Faster CPU, more RAM, bigger screen. But, of course, we won't be able to buy it.
I've been looking at new phones for quite a while, and can't find a better phone for me. One of the reasons is the keyboard. Another reason is that the N900 is the only phone that i know that is quad band GSM and has both AWS and 900/2100 3G. This is very important to me, because while I live in the US, I go every year to Europe, and I don't want to use two different devices if possible.

So the way things look, I think I will keep my N900 as a phone for a few more years, but probably also buy some sort of 5" Android (or Linux) PMP/tablet thingy for stuff like videos (which really suck on the N900 screen).