I've actually been looking at reviews of the 17-85, and most are saying it has too much distoration and color issues from 17-24 mm. I'm now tempted to stay away from that lens. I will probably compliment my existing 28-135 with a 17-40/4L. I also think the 17-85 is over-priced.
Glad to hear you're liking the new lens Dean. Did you think of purchasing the 17-55 f/2.8 IS? Have you compared them at all. I've been thinking of replacing my 17-40 with the 17-55.
Honestly, I'd go with the EF-S 17-55 IS. But if you want one of the above I'd go with the 17-40. It's a nice lens, not perfect but very nice. The 17-55 is more expensive but it is much more versatile and is an f/2.8.