The new driver fixes connection issues for some people but has a pretty severe regression causes very high latency/jitter for many users (even pinging local router gateway wildy fluctuates between 30-150ms ping. many,many other posts in the apple forums verify this too. As soon as I manually downgraded the driver everything started working well again and latency is now 1-3ms to the router as expected.
Right now there's two options: The original driver which seems to work perfectly for some, but seems to have connection issues to certain AP's, but always has stable latency, or the updated driver which has less connection issues but awful, awful latency and jitter. I really hope they release another update that fixes these issues properly... I really love my new macbook air aside from this issue, I had hopes moving to apple would avoid these types of issues :/