I chose the 17-40L as my main lens for the 20d I just got.
The reason for this was to me pretty obvious. First, if I got the kit with EF-S 18-85 lens, the cost was 2K. If I got the body with the L glass lens, the cost was 2,080 - or 80 dollars more to get a quality L glass. And the L lens came with the hood and bag - something that the 18-85 did not, adding additional cost.
Secondly, I shoot primarily wide angle - taking landscape photographs. Sharpness at the wide end was a most definite requirement. While I've read some good things, including on this site, about the EF-S lens, I've read many better things about the 17-40L here and over at photography review.
Third, the L glass works on my Elan 7. The EF-S will work only on the 20D and other Canon cameras that may happen to use this mount in the future. I saw no point in getting a lens that only works on the 20d when at some point it seems likely that I will want to get (may be a few years down the road!) a full-frame camera as their price comes down as it inevitably will.
As for telephoto, I currently have a 2.8 100mm lens which of course becomes 160mm on the 20D.
And for only moderate telephoto work, I find that the f1.8 50mm lens works just fine.
Just my two cents.