Well, I upgraded to the S2 IS. I came close to going for a digital SLR, but I cannot justify the cost, the larger size, and the need for additional lens' etc. For now at least, I like the Canon S1/S2 camera's for the long IS zoom from wide to zoom and the video mode. I would not have that on a digital SLR, and it would be bulkier. In the future, I may go with a digital SLR though. It is getting tempting with the lower noise CCDs and prices dropping.
My S1 IS is now for sale for $390 CDN. Comes with original box, manual and compact flash card, av and usb cable and additional 512 MB Sandisk Ultra II high speed (60x) Compact Flash card.