I've had my N810 for just over a year, and I too enjoy the heck out of it.
I'd be willing to do whatever I could (and had time for), but I am a sysadmin rather than a programmer...
As for what I would like to see, I have a core cadre of apps that I use, which is everything from FBreader (I read on it a *lot*), MediaBox for media playback (mp3/ogg in the car, movies at other times), angband, tear and midori for browsing, the list goes on.

The main advantage to the N900 from my perspective (other than being new and shiny), especially since I had an AT&T rep tell me that an N900 wouldn't work on their network, is the additional onboard storage and the faster processor...

--vr