I would give almost anything for a sharp, reliable 50mm lens like the 35 IS
Same here. I'd be ok with f1.8 or f2, but would really like a 1.4 version w/ IS. That would be a killer walk around lens for me. And, I think it could be similar in size to the 35mm IS, when looking at past lens sizing (I.e. 35 f2 vs 50 1.4), but I'm no physics expert
I am also a Huge Fan of my 35 IS.
Actually, I think a 50mm f1.8 IS would at most be about the size of the 35 IS, perhaps a bit smaller and less weight. (but I'm also not an optical engineer).
This may be heresy, but if you "only" make letter size 8.5x11" prints, the amount of cropping to turn a 35mm into a 50mm won't be noticed. Even with pixel peeping, my impression is that you would have to be relatively experienced and know what to look for to see much, if any, difference.
Further, my understanding is that there is NO scene that can be captured with a 50mm that a 35mm can't capture (with relatively minor cropping and NO zooming with your feet). The opposite isn't true. A scene where a 35mm FOV is perfect would take some compromises with a 50mm, if even possible (like can't back up).
So? Get the 35mm ... yesterday ... rather than waiting another 12 to 18+ months for a rumored 50mm f1.8 IS to come down from an introductory high price for pro's and well heeled early adapters, to under $500. Obviously, a f1.4 would be a somewhat more $$$.
And with minimal pano skills, my 35mm IS on 6d can become a "poor man's medium format camera with a very wide angle lens" (not uwa) with 10000+ x 3700 resolution in portrait mode. I'd think such a capture would be darn close to as sharp as a Pentax 45z with a native, prime very wide angle. Or not?
Note: pano-head and tripod recommended for interiors, and for scenes with prominent, large foreground is important. I've been using my pano-head less and less with some attention to detail to reduce stitching errors.