new walk about lens?

Currently use a 17-85.Was considering a 24-70.How does the 24-70 perform on a 450d?Any other suggestions?

The 24-70 is going to be a bit heavy on the 450D. You will get better IQ, but will lose the wide angle capability.

This was my setup for about a year. It was a bit unbalanced but not untenable. I was happy with it.

Ya that 24-70 is pretty big, I would think a grip on body would work well with it.

I used a 24-70 on a 350D for the last 4 years. While it's a great lens especially for low-light/shallow DOF, it's not wide enough on a crop body and I end up always swapping with my 10-22mm. I recently bought the newer EF-S 15-85mm lens and it's been great so far. Much better as a single-lens walkaround solution, imho.

Another option if you want the speed of the 24-70 but more ideal for crop bodies would be the EF-S 17-55mm f/2.8.