This article is about lean and I really like and want to like lean. But... At the moment it bothers me that the authors still consider it an experimental engine

This article is about lean and I really like and want to like lean. But... At the moment it bothers me that the authors still consider it an experimental engine. In this case it means development stopped on version 3 when they started version 4. No bugfixes, no enhancements are accepted into version 3. When/if they make the mental switch from experimental to a supported product, I'll definitely use it and maybe even contribute to their proof library (if there are low hanging fruits left).