Don't go back to 3.0, IMO the server options make the game very boring to play without the ability to randomize gameplay types, and 3.1 includes multiple bugfixes.
Anyone who's still on 3.0 (there are still a few people) really needs to pay better attention, there's plenty of info about the fact that there's a new patch out on the main page, the wiki, facebook, moddb, youtube, and many other sites. It's been out for months now.
I expect another explosion of activity with the Beta 4 release, as from what I understand it includes a lot of things I hear people complaining about on a fairly regular basis (Facility Backzone, rolling explosions, and maybe dual weapons, but I'm not on the dev team so I don't know the true status of that).
You're better off on Beta 3.1, some servers can reach full capacity around 8:00 PM EST from what I've seen.