I bought the 35mm f/2 just before a trip to Ireland. Here is
a review I read on it. Center sharpness is good, but they complain about corners, and say there is vignetting. I haven't noticed this, but I use a crop body not full frame. It's got a very noisy autofocus (sounds like a buzzing bee when hunting) though.
I'm not a real expert (my other lens is the 18-55mm IS) but I like the photos it produces. You can see a few samples here:
http://www.mikepirone.com/gallery/Guinness/IMG_1554
http://www.mikepirone.com/gallery/Guinness/IMG_2099
http://www.mikepirone.com/gallery/Guinness/IMG_1584
http://www.mikepirone.com/gallery/Ireland2009/IMG_1947 (shows the bokeh)
Also, if you decide you don't want a prime, there is the bank breaker 17-55mm f/2.8 IS, and the Tamron 17-50mm f/2.8, both of which are highly regarded at
Photography-On-The.Net