First of all, thanks for finally sending me a key. I applied for the beta ages ago. 
Performance:
Intel i7 3770K @ 3.50 GHz
EVGA GTX 660, Driver 347.25
16 GB RAM
Win7 64 Bit Pro
I played on default settings, but I turned off things like blur when sprinting and other vision inhibiting visual effects. The performance was reasonably good. I got no major FPS-lags even without using V-Sync, which is surprisingly good. The game ran quite stable throughout the 8 or so hours I managed to play this weekend, though I did experience one CTD when playing on a server today and the game was about to switch to a new game at the end of a round.
Hit-registration and general network performance seemed fine (running on 50/5 MBit cable). I noticed a few minor lags when strafing along a wall while scoping, though. Might have something to do with collision detection. But I am generally very happy with the way the game is behaving. A feature like a lagometer in Quake Wars would be nice so we could see where and when we’re actually losing packets. Please correct me if there is one.
Gameplay:
I managed to explore only a few of the classes so far, but liked what I saw. Especially Aura is great fun to play. The healing station is quite powerful, but I’d disagree with various comments that claim it’s overpowered because it’s very fragile and can be shot/grenaded easily if you bother to do so. Class balance is hard to describe so far because all classes can complete objectives and all classes can revive, though some are obviously better suited for certain jobs.
This is where I see a major problem so far. I’m not sure I like the fact that you can select only three Mercs, and on top of that you can’t really tell which one the other players will be playing, so there is no way of getting a grasp on your team’s class disposition before the match starts, which is problematic because that is the only time you can make changes. Further, I don’t like the fact that you always spawn as the Merc slotted in the first position and sometimes you enter the game and have to respawn before you can play the class you want to. You should always get the chance to change your class before spawning for the first time so you don’t waste time running a class you don’t want to.
As far as the loadout cards go, I feel they are sometimes a bit hard to distinguish. I noticed that when I started playing as Vassili for the first time today and wanted to check out the different loadouts and ended up fussing around with them, not being able to tell which was which and which I had already tried. Perhaps showing names of the loadouts on the cards would help to differentiate better between them.
The wall-jumping seems like a cool little feature and I’m looking to forward to discovering what trickjumps there are. Though what I do not like at all are certain invisible walls that prevent you from jumping to certain places even though they would be otherwise accessible. This is a clumsy way of limiting player movement and should be either removed or handled differently. Also, I managed to get stuck in mid-air while jumping off the wall on the very far left corner on Chapel behind the EV on the first objective. I jumped off the wall and the crates, and then remained stuck in mid-air as if in mid jump.
On another note, please let players sign up on the forums with a name of their choice without having to download third-party software to change it from some silly random name. That’s not cool at all.
That said, I’ve enjoyed the game very much so far and hope this turns out well in the final release. Good luck with further development, SD.