Sorry should have been clearer. I am getting the 24-105 and wanted to get one more lens to go along with it. The 50 mm just because it is sharp, cheap and good in low light, or the 10-22 for some more creative fun shots. I thnk I would have more fun with a wide lens than with the 50mm.
I was hoping that some people here might have some awesome shots taken at 10mm which would have sold me on it.
I had a play with the sigma 10-20 in a shop the other day and it was a nice lens. I am just slightly put off by the fact that most forums are filled with people who have had to send them back because they are soft on one side of the lens. I have also seen some comparison shots between the sigma and the canon lens and there seems to be quite a difference between the two.
Then again, if I get the sigma, I can get the 50 too.... could really do with a lottery win. Would make this so much simpler.