I'm quite excited to see an actual lens announcement from Canon - and well done to CR guy for predicting the 24-70mm L f/4 IS USM.
As I don't plan to go full frame (at least not in the near future) - the 24-70mm L f/4 doesn't interest me so much. I'm very happy with my 15-85mm IS USM on both my 7D and 350D.
If the 24-70mm f/4 L has great IQ, I can imagine it will be popular as a less expensive / less bulky walk around (aka 'kit lens') for some folks having a FF, perhaps particularly the new 6D. (though I will say here that a possible price of $1800 USD is quite scary!)
To me, the 35mm f/2 IS USM is actually a much more interesting lens... and.... in one sense meets a lot of the criteria I have for the 'only lens' that I'm really looking forward to, or - that is what I find 'lacking' in my current lens arsenal: a sharp prime at about 50mm (+/- a few mm).
The new 35mm has the following features, which are important to me:
- USM - my preferred AF mechanism, with FTM focus
- 4 stop effective IS
- 7 or more blade circular aperture
The size of the 35mm f/2 IS USM is still small enough. I guess any 50mm would be a bit longer... possibly could have 58mm or 67mm filter size. (I hope if a 50mm prime comes out, that it has a 58mm, 67mm or I'd even 'put up with' a 72mm filter size - as I have filters for these sizes).
I expect the IQ of the 35mm f/2 to be very high (better than the 40mm f/2.8 pancake, which has received lots of praise, particularly for its price!)
My 'only' concern is that the 50mm might be a f/2.8 lens.. (no, please, no!) I had already decided that f/2 is perhaps the limit that I'd be happy with for a 'fast prime'. Obviously f/1.4 would be ideal. With f/1.8 or f/2 being 'good options' - particularly if IS is included.
There would be some situations that 35mm is more suitable than 50mm (eg some group shots, etc). However my own photography style, means that I really like the 50mm aspect on an APS-C (giving the equivalent of 80mm in FF format).
So... now that the 35mm f/2 USM IS has come out (after the 'earlier this year' new 24mm & 28mm f/2.8 USM IS lenses) - I have more hope that a 50mm f/1.4-f/2 USM (possibly IS) lens will be released in the near future. I plan to go to a bricks and mortar shop and use the 35mm f/2 USM IS sometime.... see how I like it, get a feel for it, and hopefully see a new 50mm prime in store sometime in the future too...