I just moved up to a Canon EOS 20D from a Pro90IS. It's like night and day. The 20D will shoot 5 frames a second (sounds like a machine gun!). Focus is virtually instananeous. Noise is almost invisible at ISO 1600. Just as a test, took a couple of available light indoor shots the other night. They look pretty good, considering I just opened the box and am still learning the camera.
I love the "kerthunk" of the shutter :-)
Lenses are costly and I'm sure I'll need more as time goes on. I guess there's a difference between taking pictures and photography.