I'm just catching up on this discussion. I think Trae has made some excellent points. If I may add what may come of as snark to some folks here, I will just note:
* Why does it have to be one theme? If 4 or 5 themes shipped with Drupal, average non-technical users would have some quick options. Fixed and variable alternatives could be offered. (I'm not a fan of fluid themes b/c of problems with readability, but that's just my own view.)
* This thread on /theming/ has gone on for the better part of a couple of days, and not once has it been brought into the themes discussion list, which begs the question of how themes are to be evaluated, developed, etc. Just sayin'.
Personally, I don't care at all for Bluemarine but have no big problem with the other core themes. I also like Box Grey enough to not hold its tables against it. ;)
Laura