The current pre-release of the client ("pioneer" in the version) is only compatible to itself. So you can only play with other testers. Please be aware!
@Draiget Awesome! I was thinking in terms of large maps + lots of players + lots of units and how it tends to slow down player's CPUs, and thusly the game itself as all players can only play at the speed of the slowest CPU. You're saying that's been improve 43% which is a huge deal.