4.3 brought major changes in the vt-x code for stability and performance improvements.
You should look at the change log and source code commits.
It wouldn't surprise me if 4.4 gets released soon with a new batch of improvements. 4.3 will then get put into maintenance mode and 4.4 because "unstable". I normally don't deploy the current branch in production for several releases as they fix the issues.
Project development is far from a standstill. I don't need any more flashly features. I hope they continue to focus on stability and performance issues.