I am using a N900 as my main phone for two months now after using it mainly as a small Emacs/org-mode PC. Got frustrated about my Samsung galaxy android phone after owning a G1 for a few years. I really missed the keyboard. Had my eye on the N900 for a long time, but thought it had a dead OS due to the shift from Nokia to Windows Phone. I took the plunge after reading about Emacs for N900 and Easy Debian.
I should have bought one years ago - it is still an amazing device and everything it lacks is fully compensated by its uniqueness. Definitely not a phone for everyone but it suits me greatly.