I have the Canon SD800. I have had two SD series camera prior to the 800. The 800 is awesome since it has optical stabilization built in, 28mm lens and 7 meg pics. My last WDW trip in OCt we took the Rebel Xti and the SD800. We took a bunch of pics with both cameras. The SD800 takes amazing pictures, including night shots. I took pics from my seat at a recent Aerosmith concert and had some experienced photo friends believing i had taken them with the Rebel. I can post some or email if you want an idea.
My best shot I took with the SD 800 (in terms of memories, not setting) is my daughters first ride on Aladin's carpet ride. She sat up front with my wife, so I held the camera out to the side even with them and snapped the shot (no way I am doing that with the Rebel). One shot she looked to the camera and it looks AWESOME.
As you can tell, I am a SD series fan. I like having both cameras being Canons since the menu system is similar.