For £100 more you could pick up the Canon Powershot G12, released at around the same time. For your extra money you'd get a larger zoom range (5x with the Canon G12 vs 3.8x with the Canon S95's 28-105mm equivalent), an optical viewfinder, a vari-angle LCD screen and better battery life.
In our Canon G12 review, but to compare the specs on paper, it would seem as if the smart money would be on the Canon G12. £100 for all those extra features does seem like quite a good deal, but bear in mind this effectively takes you from a discreet pocket-friendly camera to a bulkier and heavier design perhaps slightly more suited to compact upgraders than as a handy DSLR backup.
It's also worth considering that the Canon S95 uses exactly the same sensor and ISO range as the Canon G12 while also offering a larger aperture on its lens (f/2.0 compared with f/2.8).