What the 35 / 2 IS has done for me, and, more specifically, Canon.

Most reviews indicate that in body IS is less effective than lens IS at longer focal lengths. I don't think I'd want to see Canon go to in body IS instead of offering a 70-200mm IS or 400mm IS lens for instance. At 35mm it would probably be fine though.

I recently purchased an Olympus E-PL5 with in body IS. It's a fantastic camera, but the IS is unreliable and often results in blurring at shorter focal lengths and what should be safe shutter speeds to not need IS. I've had to turn it off unless I know that I really need it, which is a pain and I unfortunate to have to worry about. There are some discussions on this issue in the m43 forum. The shutter vibration on many of these cameras causes this.

So, all is not rosy with in body IS. I wish it were, but I sure enjoy worry free Canon lens IS after this experience.