I just sold my G10 to get a DSLR. Not because the G10 is a bad camera or anything, it's just that I have found myself in a situation where I need a DSLR to do the things that the G10 simply cannot do. I am shooting more indoor sports photos and photos that require higher ISO performance and more DOF. Here's my opinion...
Buy the G10 if you plan to ...
1. Shoot outdoor landscape photos or general shots in good lighting where background blur behind the subject is not important to you.
2. Want a small portable camera for excellent macro shots.
3. Want a camera for the above that you can easily carry around with you.
Don't buy one if you plan to...
1. Capture any action or sports photos indoors, it's just not gonna happen with good results.
2. Shoot at high ISO's
3. Replace your DSLR and expect it to perform as well in all conditions.
I loved my G10, but I'm shooting different things now and I need a fast shutter and low light performance. The G10 does have DSLR like features like 1600 ISO but not the performance, and I think most people know that going in but some don't and are left dissapointed. One thing that is great about the G10 is the ability to see on the screen what is happening when you make adjustments to ISO. shutter speed, and aperture in real time. This allows a person who is just starting out to see how one is affecting the other and helps to you gain a better understanding how to adjust ANY camera for proper exposure. The G10 is a great learning tool for a beginner and a sufficient "backup" for a DSLR user in the proper conditions. There is no question in my opinion after owning one the quality is outstanding at low ISO's in good lighting conditions. I had a blast with it and I would recommend it to anyone looking for what is probably the best P&S around, but KNOW it's limitations and what you will be shooting mostly.