Oh, maan... I still remember my 5800, I loved that phone to pieces... Excellent speaker system for the time (it was genuinely stereo and had a bit of meat on the sound, too!), my first touchscreen (which was a bit frustrating due to my thick logs, but worked perfectly with the stylus), and it was also my very first experience with multiplayer on a phone! Used to play that default racing game with a year mate in Uni, and it was very fun! And the OS was as an OS should be: so smooth as to not even register with the user!

Edit: oh, and the full QWERTY was very nice, although I was fresh off the keypad, so it was a bit awkward.