So far, I quite hate the forum changes. I have no hard numbers of course, but I'd guess a lot of people interested only in Legacy or Pathfinder feel crowded out by Next (that was my gut reaction, at least). Took me a while to notice you could click on the tags to filter threads - maybe some regulars won't even find out? Posts and new topics seem slower than before the change as a result. At the very least sticky a message at the top of the "D&D and Pathfinder" sub-board!
Furthermore, what the change did was not encourage synergy IMO, but encourage heavy usage of tags. So now I'm looking only at 3.x, instead of all Legacy. To look at earlier edition stuff, I have to do several clicks, each of which takes a few seconds. In effect, I'm not looking at more content at the same time, but less. You just split the forums further! Tags are just a different way of lumping threads together!
How about lumping "current" (Next) and "former" (everything up to and including 4E) editions of D&D each in their own categories, and do away with the tags? That way, I'd really look at more threads, and be tempted to post in more of them, at the same time. Also, bring back the "General" forum for topics like problem players, playstyles, theme music, story telling etc.!