I used my 17-55 in the Sistine Chapel which is about as low light as i've ever taken pics... most came out very good. Its super dark in there and there's signs every where that say 'No Flash Photography'... needless to say, flashes were popping off every 5 seconds or so and the attendants in the room didnt even try to to stop anyone. I didn't use mine once (outta respect). I always try to lean against something for added stability.


btw - if you use a monopod with the 17-55 IS, you have to switch off the IS anyhow