Well, you already know that John, Carla, PJ and I vote for Mac.
Here's a cool thing about photos and iPhoto on the Mac that never fails to impress my non-mac family members when we get together at holidays, etc. I just take anyone's camera (and there are old and new, Canon, Olympus, Sony, Kodak), connect it to my PowerBook and iPhoto recognizes the camera and loads the photos. No setup, no extra software, no hassles. Collect the whole family's holiday photos, burn CDs, and everyone has the shots that they may have missed.