Hello! I have decided it is time to upgrade from my kits lens (18-55mm) for my Canon 50D. (I use it often indoors with low-light situations) I have narrowed my selection down to 2 lenses that are in my price range that are close to what I am looking for: Canon EF-S 17-55mm f/2.8 IS USM Zoom Lens ($1080) -or- Canon EF 17-40mm f/4L USM Lens ($750) My problem is this: The first one is in the range I am comfortable with , has image stabilization and opens to 2.8 which is good for me because I often have to shoot indoors with low-light. The second one only opens to 4, (and only goes to 40mm) but is an L-series. For the canon people out there, is the "L" part of this going to make this lens better than the first one? Even though the first is more expensive? And is image stabilization all it's cracked up to be? I have it on my 70-200 and love it, but do I need it for the wide-angle zoom? I guess I'm wondering if it's kind of like "cheating" and doesn't really work that well. Thanks so much!