@wickedwombat: I did some experimentation with m/sRAW today. With just a minimal amount of fiddling, I was able to make the full-size RAW scaled down to m/sRAW size look pretty much just as good. At higher ISO's, noise looks different, often better, because its coarser...it looks like there is less of it, even though its roughly the same.
One thing I did learn, however, which has turned me off of m/sRAW a bit...is that it does NOT behave like a real RAW image when you need to make any kind of extreme adjustments. In Lightroom, if I adjust exposure settings, curves, noise levels, etc. more than a medium amount, the m/sRAW formats start to show their limitations. The problem there is that they have already been demosaiced and converted into RGB pixels. RGB pixels do not have nearly the leeway the original bayer pixel data does in a true RAW image.
While I think there are some benefits to using both mRAW and sRAW, particularly the clarity and definition of details (which gets preserved better with those formats strait out of the camera than with the native raw), if you want to preserve the ability to recover highlights and boost the darkest shadow tones, you'll want to keep shooting in full RAW. Perhaps a format can be created in the future that will behave like a RAW while making better use of bayer pixel data, but for now, m/sRAW definitely have their limits.