I just did a survey on their official website and got the invitation on my mail one day... There are plenty of ways to try to obtain it though. Survey on the official website is still there for you to do and a lot of people are giving away keys on steamgifts.comGrr hex >.< I've been trying to get into that beta forever . How did you go about doing it?
Also, games i'm currently playing right now: Skyrim, Gears of War 3, League of Legends, and Batman: Arkham City