The N73 is faster, has a much better camera, has a much longer battery life, a larger screen, stereo speakers, and I found it to be more stable, though I'm sure the N80 had enough firmware upgrades to make it stable as well.
I was completely satisfied sacrificing WLAN for all the benefits of the N73. The joystick sucked, the keypad was sketchy, but it was still a much better experience than the N80.