If you really want high quality indoor/low light photos, then obviously a D-SLR with external flash/strobes will be the choice.
None of the compacts will give you very high quality low light photos. You need to keep ISO at or below 200 to get the best quality. Anything over ISO 400 will look grainy and unappealing. Some models do better than others, but I haven't seen any compacts (including the Canon G series, S90, Panasonic LX series, etc) to have very good output above ISO 400. That means you need to use the built-in flash or external lighting when in low light to get good quality photos. Although built-in flash will give you the overexposed foreground and underexposed background, I will rather have this PS style photo than to have a blurry grainy photo at high ISO without flash. You can easily fix shiny forehead, red eyes, even underexposed backgrounds. But it is impossible to fix a blurry grainy high ISO photo.
The Canon S90 is a very good compact. I have the G10 because I use external lighting (bounce flash or the Litepanel Micro) that can fit into the hotshoe (the S90 and Panasonic's LX3 do not have a hotshoe). I can get photos close to D-SLR quality with external lighting, when keeping my ISO at 200 or below. Even at higher ISO (to expose the background), the foreground subject still turns up pretty well with external lighting. However, many compact user will say that the external lighting is more bulky and more expensive than the compact camera. It is true, but it is still much lighter than my D-SLR equipment.
So if you want better quality photos with a compact in low light, then the Canon G series with a hotshoe will do better than the S90 (only if you carry external lighting). My G10 with a Canon Speedlite gets better photos than my friend's S90. But if you want to be a minimalist and carry as little weight as possible, then the Canon S90 is definitely lighter.