I find the 17-85 very satisfactory. I use it when I want a walking around lens or really want to travel light.
If you are expanding the long range of your lens, consider a 70-200 or the 100-400. Both are excellent additions to the 17-85 on the long side.
On the wide angle side I am finding that the 10-22 is one of my favorite lenses. Its super wide angle provides a very compelling perspective. It is sharp and has a very good IQ.
If I had a 17-85 (which I do) I wouldn't trade it in for a 18-135 (and I'm not going to!).
However if you wanted more zoom range and you were buying into the EOS system for the first time with something like a Rebel T1i, then the 18-135 wouldn't make a bad first lens.