9 out of 10 points and recommendedSize, sharpness wide open, bokeh, focal lengthNoisy, plasticky, focus-by-wire, exposed front element, price
Optically, this lens is like Mary Poppins: Practically perfect in every way. It's razor-sharp wide open (sharpenss is almost always limited by focus accuracy and camera handling) and has nice, smooth bokeh. The 40 mm focal length is just about perfect for a day-to-day lens, especially indoors. It shows little to no signs of flare or glare (with an aftermarket hood). I've shot straight into lights 5+ stops past being blown out, and never observed a flare. Fundamentally, I love the lens because I never need to worry that the lens will let me down optically.reviewed August 17th, 2010 (purchased for $400)
It's also tiny, which makes it exceedingly easy to carry.
The focus isn't all that brisk, and it's not exactly silent. The focus-by-wire system (common to all mFT lenses) makes manual focus less pleasant than it might be.
Build quality is adequate, no more.
Without a hood, the front element is very exposed, and given is propensity to be pocket-carried, this is a little unnerving.
This is not a cheap lens by any stretch of the imagination. However, twice its purchase price would be insufficient to part it from me.