Well, my philosophy was this:
1. Buy once, buy right
2. Glass before bodies
3. Allow for the possibility of upgrading away from crop body
Hence, I started with a 400D twin lens kit, and over a period of 3 years replaced the two lenses with 70-200/4 and 17-40. Yet, I do not suffer "L lust" nor am I motivated by my ego in any of my purchases.
The 17-40 goes very nicely on my new 5D2, whereas if I had bought a crop-only lens instead, I would now be up for another $1,200 to replace it with something more suitable.
our philosophies are different...mine is more of a buy for what you have now...
if you had bought a crop only lens i'm assuming you'd just sell it and get something more suitable...maybe you'd be out $100...which isn't that bad over 3 years time...and you'd probably have shots that you couldn't have gotten with the 17-40mm
when i say L lust i don't really mean it as a bad thing...i think people see the 17-40L and think...it's an L, it's the focal range i want...it must be the best option...i'm not sure that it is though