Thanks I'm shooting the 1d Mark II so the EF-S lenses are out but I should have mentioned that before. (my bad) The only prime I have right now is a sigma 20mm which I purchased for shooting interiors of buildings. So the primes you mentioned are high on my list. I was looking at a 85mm that has...

Get the IS. You can find people who look at their pictures at 200% and find imperfections and claim the IS is worse, blah blah blah. The truth is that Canon's IS is outstanding if used properly (setting 1, or 2?) and it will save lots of images you wouldn't have gotten otherwise. Here is an example...

I shoot with this lens, and find it rather delightful. The IS helps a lot, and the aperture is still wide enough at the large end for excellent portraits. This lens is ideal for hand-held shooting.