Build your own traffic shaping router based on FreeBSD
FreeBSD 7.2 has been official now for a couple of weeks and no major problems have been reported. I'm preparing to upgrade my own router soon and I will start adapting the guides to 7.2 some time after that.
A preliminary release date for FreeBSD 7.2 was announced today and set to May 4th. Fixes for the UDP deadlock has been submitted to FreeBSD-STABLE but we're still waiting for an errata to FreeBSD 7.1. Going directly for 7.2 when it's available is probably a better idea. It's worth mentioning that there has also been several reports regarding an inability to boot after upgrade to 7.1. There was an upgrade of FreeBSD's boot code for that release but there's still no consensus on what systems are affected.
Although FreeBSD 7.1 has been available for a couple of weeks now I suggest you stay with 7.0 for now. According to this thread on the freebsd-stable mailing list, there seems to be a regression in the UDP protocol leading to deadlocks during moments of heavy traffic. I will update the guides here when this has been sorted out but for now you should use FreeBSD 7.0. Media for both the i386 version and the amd64 version (as well as all the other supported platforms) can still be downloaded from the ftp.