Good value but I would invest in the 16-35mm f/2.8

Now hear me out. I know this lens runs around $600 and the 16-35mm f/2.8 is twice that for $1200. First off... if you're shooting with something like a 20D and it's not full frame (1.6x) you're getting a 27-64mm. So going down to 16 for that wide angle is key. Second, the f/4 isn't as flexible as the f/2.8 in low light where I love using this lens. If you're like me, and typically carry only 2 or 3 lenses. You want to have one that low light and wide angle. Sure you can go fixed and get something even down to a f/1.4 but then you have to carry more lenses. Save your money and get the 16-35 f/2.8 and carry les lenses. You'll thank me later. That being said... this lens is awesome. Great range. f/4 isn't too bad and the clarity of this L series lens rocks. I wouldn't hesitate to use it and capture some amazing shots. The 17mm gets a little distorted around the edges of the picture. But not too bad. Depth of field with this lens is very nice as well. Creates great smooth blurs that you don't get with cheap wide angle lenses.