Have you considered the new 24mm TSE?
Indeed, that is where i started, but drifted away from it as i do like AF for quick street/environmental shots.
I think I'll be adding the 24 2.8 IS to my collection next for use on a crop body, my main reasons being the compact size and low weight, the low light handholdability and the ~40mm equivalent focal length, good as a walkaround lens.
This is also a consideration for my wife, she is getting a 100D... hmmm, I had narrowed it down to two and now i'm back to three... on the bright side, at least i have a choice and the money to spend on it too... damn these 1st world problems!
Thanks for the input, i think I am more leaning towards the 24-70 (+ new CPL filter, sigh)...