A friend of mine matched his 7d with the Canon EF-S 15-85 3.5-5.6 IS USM. Seen here:
http://emedia.leeward.hawaii.edu/fra...n_efs15-85.htm
It gives stunning IQ results, maybe not up to L series standard build wise, but one that was built for the 1.6 crop factor. Why put lenses on your camera that were originally built for 35mm film and not digital?