Pretty similar to the Canon 24-105 L, but with better centre resolution...
EDIT: Sorry, forgot to post the link -how rude of me!
http://www.photozone.de/canon_eos_ff/864-sigma24105f4eos
EDIT: Sorry, forgot to post the link -how rude of me!
http://www.photozone.de/canon_eos_ff/864-sigma24105f4eos