We actually have been trying to keep stable working. But for some reason, the last stable that we made doesn't work anymore, even though I'm positive it did for a month after we released it. I think it has to do with mingw-get. This would probably be consistent with why it worked for a month and then suddenly stopped working - mingw-get now fetches incompatible targets.
Moral of the story, don't blame Stable, blame mingw-get.
In the meantime, I've defaulted the checkout to always use Trunk until we can get Stable sorted out (but waiting on JoshEdit until I can commit that change). Translation: I've hacked out some of the burnt pieces, but it'd be awfully nice if we could figure out why we're burning this fish, because otherwise this is just going to keep leading to more and more burned parts being hacked out until we're left with dregs and morsels of an installer/updater.
I will mention that the build process is officially documented and maintained on the Wiki:
http://enigma-dev.org/docs/Wiki/Install#Windowsand has been updated somewhat recently to account for broken MinGW and such.