Having more (real) resolution at no cost is always welcome, and allows for more flexibility in post.
Seems strange to me that Nikon didn't offer a mRAW and/or sRAW on their D800. To me it suggests they're slightly out of touch with what people actually want
I can only speculate on what drives the purchasing decisions of other people. From my experience of owning alll the 5D series of Canon cameras as well as most of the xxD series as well as a Nikon D800 and D800E, I have never needed to use a small raw format ever. However I do find that the various cropping sizes on the D800 are very useful. The most useful is that I can use full frame or aps-c lenses on the same camera. This would be revolutionary for Canon. But what Canon could do is to allow DX (aps-c) crop mode on an full frame camera.
Where do I use it. Let us say I'm using my 300mm for a landscape shot accross a bay and then I spot an some wildlife where I need a longer reach. I can quickly go into crop mode and choose the amount of crop by choosing the image area thereby saving the file in a smaller raw file as well as having a faster FPS. Canon could do this but so far they haven't because their full frame cameras don't have enough MP to do the crop and still have enough MP for the frame. Someday will really high MP, perhaps all cameras will allow a digital crop size so you can get any framing that you want (maybe even square - Nikon D800 has a very pleasant 5x4 format choice that saves some Raw size).
As for the other stuff, it does not appeal to me. I dont want in-camera downscaling, cropping, or extra quantization, even if it gives me modest reduction in filesize/increases in framerate.
I know quite a few nikon shooters that would have bought d800's if it had mRAW sRAW. It's the #1 thing mentioned when i hear nikon folk asking for upgrade advice. For weddings, nikon shooters recommend the d700, d3 and d3s because the files size on the d800 is too large for that kind of work.
Here are some quotes from nikon users:
" I would look for a used D700, D3, or D3s. The D800 files are going to be way too big for your needs. The D4 is somewhat overpriced for what you are going to need."
"D3s is the leader for low light, D4 is a piece of junk. D800 is crap unless you're in a studio. Wouldn't touch a canon unless 5DMrkIII"
" Best wedding camera on the market today is the D3s. The best value wedding camera on the market today is the D700."
" I agree with Brady, D3s is a beautiful camera. Shooting with 2 32GB CF cards with one for immediate backup is a great way to shoot a wedding with confidence! D800 is a body geared towards the landscape/commercial world but not for weddings. D4 was a dud."
I could keep going with these quotes.