Which features from 0.8 aren't there?
TSM is an effort, but not never ending. We just refuse to put it out there until we've done enough testing on it to be certain about its robustness. We think the community will be happier if we wait to release it rather than rushing something out that may or may not be ready.
That being said, please test out TSM on the 0.9.6 release. I think you'll find that its performance is better than anything we've released previously (including 0.8) and so far we've been able to write far more data into it than in previous 0.9 storage engines.
I'm sorry to hear that you had to go back to Postgres for your time series storage. Hopefully our upcoming releases will give you a reason to take another look.