Just checked on Chrome here (19.0.1084.46 FWIW, on Windows 7) and seat selection works just fine. Navigation has to be accomplished via browser back/forward buttons, but that appears to work okay. It's just a little unsettling

This is the first time I've gone through the booking process since F9 changed the booking UI (however slightly, from a functional standpoint). I still want better graphics for seat assignments, though the current ones are nothing if not clear..

Fun aside: $80 is the Economy-Classic Plus delta FAI-DEN in mid-August. You can't get E+ alone for that on UA. And their seat map looks like it came out of 2001.