Well in my opinion Unreal 4 is far from being an engine as a completed project that we as developers would still be waiting to have access to as expected from all AAA engines available. I would not even consider it to be the best if choices where based on finesse of design or if awards were being give out and it’s clear with the ongoing updates that Unreal 4 will always be in some state of being in beta.
But
As part of the bigger picture I assume Epic has in mind is the ongoing improvements with community based fixes and feature additions it’s about an engine designed for developers by developers and many times postings in feedback are handled quickly and with in short order.
If the deal is that sometimes Unreal 4 does not behave the way that I expect but Epic is willing to listen as to bug fixes and feature updates our band of rebels are putting together needs then that’s a deal I can work with. If I can help them to help me then that’s a win win. 
In a lot of ways I feel Epic’s approach to distribution is unique and innovative as the engine design is future proof as to the next best thing that comes along and although “every” engine has their problems how often do the other guys update with out a total new engine version?