So, the new NetHelper plugin is very useful... for anybody not on an AT&T router. Those stuck with AT&T broadband service are unable to make use of the uPnP features of NetHelper and port forwarding is very painful.
Hamachi seems to do the trick with these users... but it's very restrictive (only allows 5 users) and is extremely expensive to remove restrictions.
That stated, there are a lot of VPN tunneling applications that are free and open source. I've looked at a few but I'm not sure what's the best way to get started with it. DynVPN seems to be the best so far (has clients for Windows, OSX and Ubuntu).
As a side note, I was unable to join a game via Hamachi but was able to use uPnP to connect to the game while a user on AT&T Uverse was only able to connect via hamachi. The host also had uPnP so we were all able to connect to the same game (was like some weird hybrid network with direct connections and connections via VPN tunneling... surprised it worked so well!).