I still have my 770 and N810 and they just don't get used much any more.

The on-screen keyboard may be a PITA but I wouldn't know as I've never used it - the N900 has a perfectly usable hardware keyboard. Even though it is smaller, the N900 keyboard feels easier to use than the N810's.
Sure the N810 has a bigger screen but that made it bulky and meant it didn't travel too much. The N900 goes everywhere with me - much more useful IMO.
The only thing I miss is the hardware button to toggle fullscreen mode for an application.