I used it professionally from 2012 - 2014, and I know of about a half a dozen companies either developing things in it or supporting it as part of saas offerings. Not that many, but each group that I know of made the switch after extensive reviews of other language options, and they've all had positive experiences so far.
Yes, I've used it for a number of academic research problems in biophysics. Our first manuscript that used it is in review right now.
To get "real work" done, I stuck with the 0.3 line. I've found it to be quite stable. Master is quite lively but should be settling down soon, at which point I'll migrate.
