Stuart, I agree with you on a lot of your points. More navigability in place of nice looking rounded boxes and white space would suit me down to the ground. I quite liked the forums on the Blackboard VLE in terms of that sort of thing.
I think one of the ideas of talkphysics is it should end up as more than just a collection of forums, and therefore the groups should end up with loads of calendar items, bookmarks and so forth.
BTW, as always very little is ‘free’ on the internet these days. It looks like there are significant limits on the ‘free’ wikidot serivce. see http://www.wikidot.com/plans .There are adverts for starters. I don’t know but I would hazard a guess that Talkphysics already exceeds their limits.