This seems to be more than a "plug-in." Even though Maya regards this as a "plugin", its a mjor effort to integrate Realflow right into Maya.
Probably will have a major impact o a lot of Maya specialists, even though it has to compete with Bifrost.
I've downloaded it and will give it a try late this weekend, and then write a quick review here. I can see a number of advantages right off the bat. For one thing, this will eliminate the problem of mis-orientation of objects when moving back and forth between Maya and Realfow. Also, competely resolves the Alembic issues. If I was just a pure Maya person (instead of having to do Realflow freelance work with MAX users as well as with MAYA users), I'd snap this up and never look back. Another thing that is advertised, but I'll have to check out, is that we can write MEL and Python scripts for RF within Maya. That could be a wonderful, wonderful feature.
So that you know, Next Limit has published this with a huge number of "how-to" videos. (To substitue for sort of a "lite" manual for the interim.)