I have a Canon S100 as a P+S that compliments my 'big' stuff.
It's pocketable with easy to use buttons and a programmable function ring on the front that you can customise to your liking.
It's slim as it doesn't rely on AA batteries. I bought a couple of spare chargable lion slim batteries and they cost pence.
In automatic / preset modes it's excellent and exposes well. Colours are nice and vivid.
I think the IQ is good for a compact of its size and weight.
If you want ultimate IQ in a compact take a look at the Canon G12 and G1X, but these are high end, chunky, and a bit ugly.
A comparison of it vs your current camera:
http://snapsort.com/compare/Canon-S1...rShot_SD800_IS
Use
http://snapsort.com/compare and then type in SD800 IS v whatever you want to compare it to. Excellent site that shows the differences in a nice clear format.