This is alpha7, as you can guess alpha6 wasn't really ready for prime time. The main problem were little build oddities and some larger integration issues with ATLAS fixed by Josh Kantor and yours truly.
Additionally I merged a bunch of other, non-ATLAS related fixes by William Stein, Robert Bradshaw, Burcin Erocal, Yi Qiang and Mike Hansen. This release will be basis for Bug Day 7 and should have been out hours ago, but I fell asleep waiting for doctests to finish on OSX 10.5. The release compiles on sage.math as well as bsd [OSX 10.5] and all doctests pass. I consider this release quite stable.
The only high priority known build issue is #1497, for which a workaround exists. So if you run FC7, 32 bit on a Dual core CPU please disable power management completely before the build. We are working on a way to detect this issue and stop the build of ATLAS with a menaingful error message.
The 183 MB tarball is at
See the detailed announcement at Google groups.