TobyMac:
I am not as skilled a photographer as many of those here and I am learning from your post. However, my experience with a broader use lens might be helpful. My first lens after the kit lens (18 - 55mm) was the EFS 18 - 135 mm Canon lens. Although this lens is a bit larger and heavier to carry, I use it as my "go to" when out looking for things to capture in pictures. It is not the magic single lens for all applications but it give a good range for capturing most things. Although I have not used one, I would consider the EFS 17 - 85 mm lens if I had it to do over. From what I have read, it is a bit shorter and a little less weight.
I hope this helps and good luck making you decision.
Dr Bob
Thank you everyone, there's some very helpful advice in here, and I think I would take the L lens in a heartbeat but for my student lifestyle its quite a bit out of my price range my I definitely have something to work on now.I think what I'm going to do is rent a couple over the next months and find out which suits me best.
I am renting this lens for the weekend -- hoping I get good results on my Canon T3i. It is a bit heavy though, but I've read good reviews on it.
I agree. I have basically the same thing.
I would suggest the Canon 17-55 for the same reasons the others did. It is about $1000.00 USD new, and about $850.00 USD used. IQ is great, it has IS, and it is great in low light with the constant 2.8 aperature. Low light is the worst (and most common) obstacles in photography. I think for your main, everyday lens, you should definitely spend a little more and get that 2.8 aperature because if you don't you will frequently find yourself in situations where you wish you had.
If you are not able to commit the funds for it, then at least be sure to drop 100 bucks on a "nifty fifty" Canon 50mm f/1.8 prime to go with your other lenses. Everyone can afford that, and it will at least make sure you have one lens in your bag you can go to when light is low. The IQ is remarkably good for such an inexpensive lens.
I have read somewhere (don't remember where) that the very newest 18-135mm Canon lens has image quality equalling the 24-105mm f/4L IS lens.
I don't know if this is true or not but, if it is - then that lens would be a pretty nice (albiet somewhat slow at the long end) walk around lens...