Criterion is a bit more mature than it was at its inception, but we still have a long way to go before I consider it to be feature-complete.
3.0.0 will be the point forward where the software will be feature-complete. At its core, Criterion is only a test runner, and should remain one that does the best job possible. Any Test API extension should, as such, be provided as an extension on top of the 3.0.0 API.
As such, the runner has to evolve from its 2.x shell, to become even more awesome than it currently is.
This project tracks the progress of these enhancements.