As expected, he says it goes better with Hungry Jack rather than the IHOP brand of syrup. j/k http://www.lensrentals.com/blog/2012/06/canon-40mm-pancake-how-did-they-do-that Actually he says it's sharp corner to corner at f/2.8 on full frame and doesn't get better stopped down.
fast glass that specs out to around 40-50mm in pancake size is a real hot item in the M4/3 community, coupled with one of the flat almost rangefinder bodies and you now have a real capable stealth mode low light party/concert concealable, bar friendly camera