My two cents worth...
I thought the tags were a good idea when I first heard about them, but now that I see them at work, I'm taken aback.
To make sure I understand the purpose, am I correct in saying that the size of the font corresponds to the popularity or number of threads associated to that topic?
If so, then I would much rather see a list of such tags in alphabetical order and be shown their associated threads when clicking on them. Or as an alternative, perhaps showing a list of the tags in order of descending popularity would achieve the same thing, while making it easier on the eye.
I've seen this sort of thing on other blogs. I've never really understood the appeal of what basically amounts to forcing the reader to sort through a mess of words. It's simply not good design.
It all comes down to allowing the user a way of find something of interest to him or her, and not what other users find interesting. But again, that's assuming I understand the purpose of the tags and the meaning of their size.
Even if I'm in the minority on this, could you at least move them to the bottom of the page? The forum topics are key to letting people know where to go for help. Finding those topics at the bottom of the page isn't the intuitive place to find them.
Thanks for taking the time to not only try to improve the forum, but also for reading this lengthy post. :)