It smells like I'm using a can'd air duster. It doesn't smell like antifreeze or mildew. The interesting part is that it is intermittent. Under normal AC operation the compressor switches on and off. It's during one of those changes (when you normally hear the small hiss) that the smell appears, and it only lasts long enough for one breath. It took my a while to get my wife to smell it. I'm going to check the pressure in the AC system shortly and see if it is lower (as I expect it to be).

-Tad