For those who, like me, were looking at the master branch and assumed the codebase was inactive, this is apparently the branch where development is happening:
https://github.com/thinkaurelius/titan/tree/titan09
This is version 0.9, and they are gearing up for a 1.0 release.
Anyone here using it who can summarize their experience? Production-readiness, performance, general usability as an alternative to other NoSQL databases?