I'm amazed with its size. The 80GB is just so thin compared to my old 60GB iPod Photo. It makes the 60 gig look like a brick! It is a tiny bit bigger than the 30 gig.
The screen is great, not only in size but brightness. I keep it on the lowest setting to save battery life but you don't really need to. The battery life is good even at full brightness.
They still have to sort out some performance issues which have been reported by a lot of users. Things like browsing through a long list of albums/artists/songs results in jumpy and laggy scrolling.
Not very nice, especially when you consider the good old 3rd gen iPod scrolled everything so much better. Even on its "Now Playing" screen, the song info is much easier to read. I take it these performance issues are a result of Apple trying to boost battery life, so they "cut corners" wherever they could. The new units go into the deep sleep mode earlier which is fine but making the scrolling all crap? BAH!
Most importantly though, the new iPods sound great.
It's great to have gapless playback (FINALLY!)