The 18-55 IS is MUCH sharper than the 17-85 IS.
The difference between 55 and 85 mm is NOT big. At the ultrawide end, every 1 mm is significant, but NOT at the normal to slight telephoto range.
Ring USM is quiet and VERY fast. But I don't think it's worth forking out so much more dough for the 17-85 lens instead of the 18-55, especially since the latter is so much sharper. And both offer IS.
The difference in the image quality between the Sony A350 and Canon 450D is HUGE. If you don't believe, you can go to the Sony and Canon showrooms, take shots at ISO 1600 and compare. The Sony A350 images are like compact digicams.
I don't understand why Sony has gone backwards to implement a 14 MP CCD when they've got a decent 12 MP CMOS sensor. :dunno: The latter is only slightly inferior to Canon's equivalent but their CCDs have always been pretty terrible.