I have the developer preview 4 and have noticed that mission control lags. In particular, the animation from when you push 4 fingers up on the trackpad to when mission control opens is choppy and sluggish. I own the 1.4ghz, 4gb ram 11 inch MBA. Does anyone have this same issue? Unfortunately I am away from home and can't do a fresh install, so I installed over my SL and I have read that the sluggishness issue gets better if you do a fresh install, but I am unsure how well I should expect this thing to run. Granted, the lion preview in the keynote was presented with an MBA, I have a feeling the sluggishness i am dealing with is only because I am using the beta. I can't foresee apple releasing an OS on a 1 year old system which lags. as a secondary note, the temperatures run hotter as well and the minimum RPM on the fan is 4.5k rather than 2k with SL. Strange.