I disagree that the 28mm f/1.8 is a dog, but it does need to be at f/2 or so to sharpen up. But the 35mm f/2 IS is only $100 more, and from what I've seen is sharp from wide open! So unless you really need the 28mm FL I'd go with the 35mm in a heartbeat over the 28mm.
If I didn't already have the 35L and want/need f/1.4, I think I'd go for the Canon IS.
Canon 35 f/2 IS

