Does anyone have a Canon EF-S 17-55mm F2.8 IS USM Lens

This lens would mostly be used as a backup for my assistant in weddings - either on a 50D or one of my 7D's

I have a 24-105 F4 - 70-200 2.8 10-20 Sigma and a 50mm - but prefer the assistant (2nd shooter) to shoot wider than i do.

Any feedback would be appreciated by those who have one...