I tried yesterday using atlas, its an auto matchmaking system. Using UNIFI 5mb, everything seems fine, no lagging found.
I still not sure how to play though. Graphic is superb, coz powered by Cryengine 3. The overheat thingy start getting on my nerf though.
The game has potential, but right now its boring coz theres only VS mode. I be happy to see capture the flag mode, and so on.

You can change weapon groups actually, just use Right Ctrl and the arrow keys to select your weapon and group. There's a pretty big post about it in the BETA forums.