Upgrading zoom from EFS 17-85

I own a 40D and in the past year updated my 70-300 zoom to a 70-200 4L and the clarity etc. was a huge improvement; I LOVE this lens. My shorter zoom I bought with the 40D was the EFS 17-85/4-5.6 and I'm wondering if I'll see the same type of huge improvement going to an L series shorter zoom. I'm frustrated at the lack of detail such as leaves on trees etc. and just don't feel the lens is sharp as I'd like it to be. I'm even considering going to the 5DII for more clarity of detail in landscape shots. Landscape shots aren't my favorite however--macro and portraiture are more my main focus but sometimes you need a great all purpose walk around. Any suggestions?

17-55mm IS - not an L because of the EF-S

but an excellent walk around lens for crop bodies, L equivalent would be the 17-40MM but I read that it doesn't perform well on crop bodies

+1 on the 17-55. It's a great lens.

If you are happy with the range of the 17-85mm, then I'd consider the 15-85mm. But if you aren't using the longer end of that zoom and have the funds, the 17-55mm is awesome.