In FreeBSD, there is KMS avaiable for radeon cards >= 5000, but you have to set the WITH_NEW_XORG and WITH_KMS parameters in your /etc/make.conf file before compiling xorg. Also, due to the limitations of syscons, starting X with KMS enabled will cause you to lose your console. Aside from that, it works pretty well and newscons should be available in the 10.1 release. I suspect this would apply to the nouveau driver as well, but you'd probably be better off using the nvidia driver.
OpenBSD has KMS support for radeon cards in current. It will be available in 5.5. Not sure of what nouveau is like in OpenBSD. The console still works when closing X in OpenBSD.
so i guess playing minecraft would work
I wasn't able to get it working in either. Minecraft in OpenBSD doesn't open the launcher. It's probably an lwjgl issue, but I don't know for sure. FreeBSD requires you to install lwjgl from ports. The launcher appears, but the game crashes upon loading. You'd probably be able to run a server on them though.