If you buy a 17-40L as a standard zoom for a crop camera now that plenty of EF-s and other crop options are available, well, you're doing it wrong. It's an ultrawide zoom for full-frame.
+1 - and that's the point of comparing it to the 18-55/3.5-5.6 IS kit lens or even the 17-55/2.8 IS. Compared to the 17-40L on APS-C, the former delivers not-too-different IQ and the latter delivering better IQ (and an extra stop of light, a broader range, and IS). Yet, many people recommend getting the 17-40L 'in case you go FF maybe someday,' which I think is pretty foolish unless 'someday' is next month.
Well, it worked for me, but that was when I bought my 10D, which was before the advent of EF-s. A year and a half later, I bought a 5D so it worked. However, if I had to start over again with crop cameras, I'd do exactly what I did at work and buy a 15-85IS instead.
That's why when I entered the DSLR world, there were fewer options out there for APS-C.
I think Canon (& other manufacturers) are dedicated to 'crop sensors' - there are still plenty of good to great lenses being produced exclusively for APS-C DSLRs (ie won't work on FF).
Hence a number of my lenses I chose specifically as EF-S mounts:
the versatile 15-85mm, superb walk-around / 1 lens-solution, with great quality and
the outstanding Sigma 8-16mm - ultra ultra wide sharp & contrasty too
I frequently advise people to get the lens they need, not 'what they might find useful on a FF'. It might happen to be an EF/ FF lens... but quite often the 'best lens for the current solution' might be an EF-S lens too!
Ok, I also have a 70-300mm L - but that's another story, as none of the other telezooms met my criteria (high optical performance, size/weight to still be portable, full USM, 4 stop IS, and zoom range). :p