so this is really sad - i put up d6 for a new site, spent a bit of time hammering away at it, running all sorts of dev and beta stage modules being ported over and then realized that soooooo much of what i'm trying to do hinges on a slew of functionality that's already up and running full steam on d5 (from views and organic groups to notifications, buddylist and countless node/content utilities)
sadly, it seems that d6 came out fast and strong with an army of busy module developers in tow, many of whom are working like mad to port to d6 but for whom 'working on drupal' is a hobby and not a full time job...same goes for the new theming guidelines, there are only a fraction of the themes currently available for d6...
as a result it just starts to feel more and more like a really, really useful version of d6 won't actually be around until next winter or spring '09 - just being conservative here, modules need to be ported, then tested and debugged, many won't even roll out for months...some module devs and teams are all over the support requests, others are sometimes around, and others appear to have walked away from modules (many looking for co-maintainers, new maintainers, listed as no longer supported or not being ported and so on)