I switched on File Vault on my 2010 MacBook Air 11 nearly two weeks ago. So far I haven’t noticed any reduction in performance. In fact, I haven’t noticed anything at all. It just works, seamlessly. Ben Brooks agrees and he has done some tests on his own MacBook Air. Result: The Air actually performs better. Like me, though, he doesn’t really notice any difference.
So pleased am I with the unobtrusiveness of the new File Vault, not to mention the enhanced security, that I am about to enable it on my Spring 2011 iMac 27. While a desk-bound iMac is less vulnerable to theft than a laptop, there is always the possibility of burglary. Since File Vault seems to have nil tradeoff, it’s an easy decision to press the button.