There isn't a P&S around that rivals an SLR for image quality. It's not even close.

Unless you're resizing images down for posting in web forums. Then even images from a 10 year old P&S can look amazing. The iPhone takes great images, but they certainly don't have anywhere near the detail of an image from an APS-C sized sensor on a typical SLR, never mind that of a FF SLR.

I'm with Mark though, there's a tremendous amount of significance to operational aspects, well beyond image quality. Any camera is better than no camera, but you can easily find yourself in a situation where the best P&S just won't get you the shot you want/need for whatever reason (slow lens, slow CPU, lack of manual overrides, etc.)