Has anyone found/done any benchmarks showing what performance impact running mod_pagespeed will have on your /server/? I'm all for optimizing the crap out of p

Has anyone found/done any benchmarks showing what performance impact running mod_pagespeed will have on your /server/? I'm all for optimizing the crap out of page serving, but if this is going to double our Apache load, a) I'd like to know about it ahead of time and b) it might be worth just applying optimizations by hand.