This is the second copy of this lens that I've owned. The first one I sold when I got my 17-55 EF-S, but I missed it so much I had to go out and buy another one.
This is a lens that I don't use very often, but when I need to take some serious portraits this little lens comes out of the bag and does what it's intended to do - produce great images.
It is sharp, sharp, sharp. For me, anything above f1.8 has been awesome, and it's very usable at f1.4. I agree with others that you need to be careful with DOF.
Many of us love to pixel peep, but I've printed some 16x20" prints from this lens and the results blew me away.