As everyone else has pretty much already laid out, the first thing you’d have to decide is whether this is the time for you to make the jump to DSLR or not. I’m eventually going to cave myself and get one, but I’m holding out to see what Canon will announce in February (assuming they follow their typical schedule).
If you don’t go with a DSLR I would be looking at Canon’s G7, as you’ve already found, or the A640. Personally, I would probably lean more towards the A640 in that match-up, actually. It’s a good $100-$150 cheaper and really doesn’t give up many features that you probably couldn’t live without. The one huge thing, though, is that Canon dropped the swivel screen from the G7, and I’m surprised how often it comes in handy using my A620 — shooting over your head, shooting candids surreptitiously, etc.
I was in essentially the same position before last Christmas, then going between the G6 and the A620. For me it came down to wanting a camera that was good enough to make me happy and take good shots but not so much that it would be a waste once I got a DSLR.
Another good resource for detailed reviews and sample images:
http://www.dpreview.com/