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

They've only just released a 24 f/2.8 IS, so I can't see them making a 24 f/2.0 IS. I'd love to see a new midrange 50mm as the current offerings are pretty poor, either an f/1.4 that's usable wide open or an f/2 that's bitingly sharp and contrasty. Can't imagine it being 1:1 though, it would have to extend a long way or become a 25mm to achieve macro focus. 1:2 ~ 1:4 might be a possibility.

As for IS, it's a good option to have, certainly, but Canon have started at the wrong end, I would much rather a 100 f/2.0 IS or 85 f/1.8 IS.

I bought the 100 f/2.8L macro to use for low light events instead of the 85 f/1.2L as slower aperture + IS ought to enable me to have more depth of field/fewer focus misses without raising the ISO. However I found when shooting at 1/25s or 1/50s that subject motion became a problem so I went back to the 85. An 85 f/1.8 IS would be the best of both worlds.

I keep thinking IS would be great for low light shots of static subjects when out and about, but then I remember in these situations I usually just tense up and rip through 10 to 15 shots in succession and I'm usually able to pull out a sharp shot at shutter speeds you would usually reserve for IS lenses.