This is just the general impression that I'm getting.
And you define “established” as…?
By nature of pricing, it will be much less used than Pro but the overlap in code is at least 90%. Mostly MVE applies to the back-end where it's a matter of “rights” for the administrator (or vendor). And in the front-end, it more like an extension of Suppliers.
So I'd say it's as established as pro but not as widely used.