Since getting my 7D, I have been struggling with the same sort of decisions. I am used to shooting FF or 1.3x crop on the 1-series, so most of that is not an issue. With the 1.6x crop on the 7D (and your planned T1i or T2i or 60D or all of the other APS-C bodies), it has been hard to settle on glass for it. The 24-70mm f2.8L is a great lens, but not wide enough with the crop. The 16-35mm f2.8L II would be a good choice, but it is heavy and feels very unbalanced on the smaller body cameras, even when using a battery grip. I did not want to think about EF-S glass, but may have to start considering those options. If you can find a good copy, the EF-S 17-55mm f2.8 is pretty close to "L" glass, has some good speed and is not too big for a smaller body camera. Most of the rest are too slow for my tastes (f4 and up), but the ISO handling can help you there. Some folks like the EF 17-40mm f4L lens, but I have never been able to find a nice copy, though I know they are out there. The EF-S 10-22mm f3.5-4.5 is pretty wide, and more of a specialized application lens, I think, but could be a lot of fun to shoot.
As you go longer, things get a bit easier. The 70-200 f4L IS is actually a very nice lens, and would be something like a 100-300mm FF equivalent, which is a nice range for most shooting, and that lens has been getting outstanding marks from folks. I cannot say, as I use the f2.8L IS variety, which is a bit faster, but also a lot heavier. Again, think about the camera balance with some of these.
Finally, a very interesting third party brand that some folks have found to be really nice on things like the 7D or T2i, is a Tamron 18-270mm f3.5-6.3 Di-II VC LD....all that mumbo jumbo means it is for APS-C sized sensors and has image stabilization (Tamron calls it Vibration Control). I was not really attracted to this option, as it is too slow for most of what I like to shoot, but folks using it for casual shooting and even video on the 7D and T2i find it to be really good, with extraordinary range and a rather decent image. I cannot attest to that, but some stills and video I have seen shot with it was impressive. And for less than $600, it can be a great all-around starter lens that essentially covers a FF equivalent of 28-430mm or so, everything one might need for most shooting. My big concern is speed, but it is light, balances well and covers a huge range fairly decently.
Personally, I gravitate toward better glass whenever I can, but honestly, now using a 1.6x crop sensor has thrown a bit of a wrench into things for me. I did not want APS-C only glass, as I still shoot a lot with the 1-series bodies, and I want good lens speed. Unless you start going to fixed focal length, those things become a bit tougher, especially for the wide angle. Just some of my thoughts on this.
LJ