Any bugs I have with mine I could live with. I do have issues relating to the short, flat, over-hard keypad, and the unsprung slide... It's now grown on me. The screen and browser are amazing, the video capture is also much better than the K800i's. It's comparable in many areas to the K800i, but is also a smartphone, and has WiFi. It is quite fat, but it's smaller than the non-smartphone SE W900i. The only phone I was considering apart from the N80 is the SE P990i, which is still not out yet.
The N80 is shorter and more compact overall than both the N70 and N90, and has a better camera too. The N91 is also huge, and has a lower res screen than the N80. You can add a 2GB MiniSD, which is a silly amount of memory for a phone. The standard music app is not as easy to use as an iPod, so I still carry my iPod as well.
Overall, it's the best example of a convergence device I can think of. There are phones that are better than the N80 at many things, but the N80 has pretty much everything, except a touchscreen and DVB-T. The N93 is superior in many ways, however, but is too large for my liking.