I would consider myself to be the antithesis of a 'Photographic Snob', and I'm all for IS standard to wide primes. I do not want to always have to carry or use a tripod and virtually all of my Building Panoramic pictures are taken just after sunrise or just before sunset so you're talking about EV 9. In these pictures I always want through depth of field, so about f8 depending, and an ISO of 100. ( Though this is not written in stone with the 6D). So my most common shutter speed is in the region of 1/20, and I can't guarantee to hand hold that speed shake free with any focal length without IS.
So from my point of view these new three IS primes are excellent. Bring on the 50 ! I guess the only reason they have not been introduced earlier is that the focus has been on zooms, which is, after all, where the bulk of the market is, but I wonder if the increase in smaller cameras is going to regenerate the small prime market.