There is a thread on the AF issue with the 40mm pancake, and to me, having to dismount and remount the lens to get AF to work (even if only occasionally) would be a very big deal.
Why hasn't this received more attention? Even the thread linked above seems to treat it as a curiosity or idiosyncrasy, rather than a real problem. It seems like a real problem to me, from what I've read in that thread...