Knowing whether you will stay with a crop sensor camera or not will absolutely affect your decisions on lens selection. The fine EF-S lenses mentioned above will not work on a FF camera, they are for APS-C only. If you are sure that you will continue to shoot with a crop body, it is not so critical. But the convenience of using your (expensive) lenses on either body should not be underestimated. If you feel that you will "upgrade" to FF any time soon, then I would suggest that the only EF-S lens you buy should be a wide zoom, like the Canon 10-22mm or the soon to be released Sigma. The EF24-105 is an awesome walk around lens on a crop, but for the fact that 36-168mm FF equivalent is not very wide.
Depends on what 'any time soon' means. The high end EF-S lenses hold their value well. I lost ~$50 on the 10-22mm and ~$100 on the 17-55mm, after 1 and close to 3 years of use, respectively. If 'soon' is next month, fine. If it's 'sometime in the future, I hope' then get the best lens(es) for the body you have now.
As the OP is about to order a 7D, I'd guess that any possible migration to FF is years away, if ever. EF-S, and more specifically, the 17-55 is the way to go. I used a 17-55/2.8 IS and 70-200/2.8 IS on crop for years, and while it does encourage lens swapping, I can't remember any times where I needed the 55-70 range.
The 10-22 and 17-55 don't hold their value that well. I lost about $120 on the 10-22mm (mainly due to a quick sale) and the 17-55 isn't bloody selling at all. Some sellers are selling it for ¥66,000, considering it's ¥105,000 new I'd say they are losing money on it big time! I'm sorry but the 17-55 is a good lens but I'd stay away from ef-s right now. Get a used 24-105L that someone is selling off from their kit. That way you can still use it on FF and if you sell it you'll likely get most of your money back.