I've recently picked up the 17-55 f2.8 IS which is a great lens. (Thanks to all that encouraged this choice). One of the things I've been shooting a lot lately, is portraits and getting ready to go out shots, of my girlfriend. (She loves to review them and calls it self-appreciation! LOL). They are shot indoors, without flash, and she will be still while I'm shooting, sometimes even striking a pose. I guess this is not dissimilar to the kinds of photos a wedding photographer would take prior to the ceremony. I usually shoot on auto ISO, hand held, and the shots are good but there can be a lot of noise depending on the lighting at the time (T1i body). I was thinking, perhaps I should get a 50mm f1.4 for the wider aperture, but then I thought... I'm already getting two stops of advantage from the IS on my f2.8 lens, so what is the 50mm really going to buy me? Is my logic sound or would I actually see some benefit from a 50mm prime?