Pros:
Most of these have already been covered here so I won't go into much detail. Screen is amazing, GNU/Linux, good battery life, etc...

Cons:
Lack of support from the OSS community/Nokia. What's up with OS2007 being N800 only? UGH. Lame, guys. The RSMMC thing is also totally bogus. I can't believe that they couldn't fit a CF card in there (4GB microdrives are cheap now). No USB host mode by default/unpowered USB port. Seriously, what gives? I understand that spinning up a 2.5" HD on the 770's power would drain your battery pretty quick, but that choice should be left to the user. I'm still also confused as to why, once I enable USB host mode and build a custom, powered USB cable, my USB flash drives won't automount. It's a PITA to have to open xterm and run a shell script every time I want to swap drives. There's probably a solution I haven't come up with yet (I've toyed with the idea of writing a status bar plugin to mount/unmount flash drives, but the whole cross platform development thing still scares me a little, and from what I've read, Python status bar plugins are OS2007 only)

(Feel free to tell me I'm nuts and offer corrections, despite its flaws, I love my 770.)