The public preview and the opt out of beta version are the current version of what is out right now.
To get on the beta tester team, you will need to email
[email protected]
There have been no new betas since may of this year while the DX11 stuff is being put in.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.