Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
read the review. also, look at slrgear and photozone.

the 17-55 outresolves all other standard zooms available for Canon (a consequence of being designed for APS-C sensors). it's shortcomings are in flare resistance and mediocre bokeh, and its color is slightly cooler than typical "L" optics. the build is upper-midrange, so high-quality plastics and no sealing. but it's not like all "L" lenses are sealed anyway. weather-sealing is relatively new, and even then, many of them still need a front filter to complete it.

it's a big upgrade over an 18-55, and i'd take it over a Tamron or Sigma equivalent or 17-40L any day. i don't think the 17-40 makes for a great standard zoom on an APS-C camera...it's shorter than usual, a stop slower, and isn't particularly sharp. all you get over an 18-55 is build, color, and USM.

A good summary that the OP should find very helpful. I'm perplexed by the statement about temperature, though, since my 17-55 definitely errs on the side of warmth, sometimes producing images with a distinct yellow cast that I have to correct in post. In this regard it's the exact opposite of my kit lens, which consistently renders colors much too cool in temperature.
 
Just out of curiosity, having never owned the Tamron, do list its advantages over the 17-40L. And the 16-35 if you've used it!

It would be beneficial for the OP too. Thanks🙂

The f/stop of the Tamron and the smaller size... add to to that the 6 year warranty here in the US....
 
If you can afford it I would highly recommend the 17-55. Otherwise the 17-40 will work for that focal range but you lose 2.8 and IS. I don't recommend 24-105 as a "walk around" because 24mm breaks in the worst spot on a 1.6.

If you do rent the two and compare them there is no way your going to want the L over the EF-S. The 17-55 smokes it in every way. I also wouldn't worry about resale. Keep the box and if you want to sell use Ebay. Canon lenses hold there value well, even EF-S ones.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.