imo, i would not buy that lens 15-85mm, but save some more money to buy 24-105mm f/4L.
24-105 is too wide for general use on a crop body, and large-heavy
15-85mm is a terrific lens, one of my favorites
, it's never been off my 60D. Touch slow, ya, but 60D has good high ISO performance to cover in most situations and you often want to stop down to near 5.6 most times for more DoF anyway. It's a great walk-around, really sharp where it counts.
17-55mm is a great lens too, not as capable IS as the newer 15-85mm but you have an extra stop worth of aperture which you can actually make use of on occasion for low light or more background blur. I rarely use mine tho, the 15-85's wide end is more useful than one might expect.
Also, if you don't really need the IS on a 17-55mm 2.8, have a look at the Tamron, the NON-stabilized version is actually a bit better than the newer OS one and IQ is pretty decent for the $ I'm ordering one for my Nikon's to sort of make up for them not having the great 15-85mm like Canon.
BTW - a friend of mine managed to nab a new 15-85mm at London Drugs in Edmonton this spring on some kind of sale for under $500. I told him to not even think about it as they were going for more than that used! He's very happy he's got one on his T2i now.