Having two primes that close in focal length to each other with a relatively narrow aperture (in comparison to your typical 2.0 - 1.4) now with image stabilization going for twice the price of a faster (f1.8) lens of the same focal length? Sure the IQ will probably be better, but it seems like a small step forward for a bigger step back.
Personally I would have liked to see at least an f2 on the 28mm. I would have jumped right on that, but with it being the same as my 24-70. I am not gonna drop 800 bucks on a repeat focal length and aperture just for IS.
And getting onto the 24-70. It had great optical quality already! Bigger filter size? No image stabilization? Booo! I cant imagine there will be a significant enough improvement in the IQ for me or anyone else (edit: without large amounts of disposable income) with the current 24-70 to drop almost 1000 extra bucks for a rehashing of an already great lens. I am pretty confused by canons recent lens release.
The new 70-200 IS upgrade made sense to me. It had better IS and truly amazing upgrade in Image quality. That is something I can understand blowing an extra 600-700 on.
It really is too bad the short primes aren't faster though. Having IS would have been nice.