I had the 24-70mm L and before that the older sigma version on my 7d all the time. I stressed about the the 17-55mm for a while, I took the leap about6 months ago, i loved and still do, the only down side to me upgrading is having to get rid of the 17-55mm.
The 24-70 produced great images I just wanted something a hair wider for my needs on the crop body. I found myself using the great sigma 10-20mm 3.5 to go wider and didn't always like the results (again for my needs) being so wide. The 17-55mm met my needs and now the 10-20mm and 24-70 L are in the bag most of the time.
note on what i use my 7d for
I shoot friends and fam indoors and out, I'm the weirdo with the massive camera at all times. - prefer no flash but keep the flash mounted for when I really want to wow people, i prefer no flash, i find everyday photo viewers like a blow out flash shot, also most people, without being to harsh are not suitable for no flash photography unless in great indoor/outdoor or great natural light. I also do photography on the side for a friend who owns a DJ company in NY. I prefer to be a third shooter, less stress I get to take a lot of pictures at events and find my shots being selected by the clients, people love the artistic/photojournalistic approach. Mostly I have them pimp me out for low stress 3 hour zap shot gigs, they have really nice commercial plasmas they put around the room - they DJ shuffles videos with the music he plays and my shots are mixed in the whole night. Its a really nice chance to get some practice and not have the pressure of say a wedding shoot. At any rate, I'm new to the forum and wanted to supply some input on how I use the 7d with the lens your considering. For a while I was actually concerned about having L glass on my 7d but Im confident and my work is suitable enough I could care less what people think about the equipment i use and always compliment me on my photos. Especialy since i wouldn't be surprised if in april i find guests pulling out there new shiny 5d3 or d800. While my camera does produce great results in auto mode in the hands of most, they always ask, why do your shots look different than mine?....