I go back and forth on this lens due to the price. But it sure does produce some great images. But then I think I should get a lens I could use on both cameras.
So I decided to hang out here while deciding
Robin, you may want to research the 17-55 for 'residual spherical aberration' before deciding. This lens has been reviewed to 'focus-shift' backward when: A.) focused very closely, AND B.) Stopped down to mid-range apertures. All lenses do both to some degree. The 17-55 can shift focus far enough to put your focused-on subject OOF at (guessing) f/4-f/8. I believe this is NOT a problem when focusing further than 3-4 feet, or when stopped down past f/8, where DOF covers the shift. See TDP's review here: http://www.the-digital-picture.com …8-IS-USM-Lens-Review.aspx.
I've been shooting full frame and aps-c for a few years now. With the exception of the 18-55 STM, I don't own any ef-s glass. I am happy with that decision.