After almost a full year of development, Haystack has been marked as 1.0.0, release candidate 1. I'd recommend all users upgrade, as it is what Haystack 1.0.0-final will be unless any bugs are found. Should all go well, I'll be releasing 1.0.0-final next Sunday (Nov. 29, 2009).
The release is available via git, via PyPi and as a tarball from GitHub.
It's been a lot of work and lots of good contributions. I'm glad to finally be in the home stretch and will post something more substantial when 1.0.0-final drops.