Indeed, I agree the system is pretty usable. I suggest you try enlightenment with the Illume profile (install e17). I had never tried it before, and it was a nice surprise, as it is elegant and almost touch-ready.
Regarding the wifi issue I have, my n900 seems to disconnect while there is high traffic on my router. May be a router issue. I am scheduled to try nm, though, to see if that makes a difference.
I am no keyboard configuration expert, but it seems the installation procedure left my /etc/default/keyboard configured as pc105. Try to change it to nokiarx51 and see if it helps. Give one example of a dead button so I can check on my unit.