When Canon sponsored me last year I used the IS version of that lens a fair amount and found the image stabilization great however it is camera powered and tends to run down your camera battery faster.
It is also a big heavy lens, but it is nice and sharp.
I'm pretty sure the 70-200 without IS is only rated at f4.
I've got the 70-200 f4 L and it really kicks some serious ass... I rarely shoot telephoto in low light... so i saved alot of money by going this route... if i was a blazillionaire, natch, i would have gone for the faster lens... as it is, i'm REALLY happy with my f4 and regardless of what you chose between those two, you can't go wrong.
As someone else mentioned however, you can get a whole other lens for the price difference. So ask yourself if you'll be shooting tele in low light.. if not, get yourself something nice with the extra money.
I REALLY desperately wanna get myself a replacement for the kit lens... I've been considering the new EF-S 17-85mm f/4-5.6 IS USM... it has everything i wanted, except a larger apeture AND L glass... the IS ought to make up for the slowness, and from what i've read, the clarity is REALLY close to L quality glass.
I'm thinkin' this will make for a stellar walk around lens... too bad no one out there is going to want to buy my kit lens.
Pat, the 70-200 can be had in the f/2.8 without IS, i have it.
I also think you can get the f/4 with, or without IS too.
Also, about the EF-S lenses. I wouldn't spend your money on one dude.
They were designed to work on cameras with image sensors smaller than full frame. In fact, they are designed for lenses with a 1.6x conversion factor. This means that if in time you choose to upgrade your Camera, it will likely have a larger image sensor, which will render your new lens useless. In fact, the EF-S lenses don't even mount properly on my 1d with it's 1.3x factor.
I'd seriously suggest saving your coin, buying a normal EF lens, perhaps spending on the L series glass, which will give you the best results for the longest period of time.
We all know lenses are where the money can be spent, i just don't want to see you buy a lens which will work well with your Rebel, but may be useless if you decide to upgrade.
I just saw the Canon 5D down at Henrys on Saturday. It is like full frame 12 megapixels but with a plastic body for nearly 4 grand. Weird. This is what the forest hill soccer moms will be sporting for Xmas....