- It passes all the test we had earlier (~ 1000 tests for Storage + 1000 tests for everything else), as well as ~ 100 new tests.
- We have fixed all the bugs found in v4.0.5 there. We run continuous integration + unit testing and measure code coverage, so we're fully sure new build is more stable than v4.0.5.
- New features provided there aren't tested so well. There are lots of them, but they're covered by ~ 100 new tests. That's the main reason we call it as RC. Another one is that implementation of some new features isn't optimal yet. Later I'll describe what we're going to improve.
So I recommend switching to this version immediately after its appearance, although you must be ready for some surprises from new parts of API.