It would be hard to say, I dont think many people buy their products because of their rep. So if they have gotten better, how would we know? If anyone has got their heads let us know how the quality is.
I've heard few people here says good thing about them. But other forum i go(Z28.com . i have GM too) people says their heads are still crop. So i don't know
i have heard very mixed reviews from the GM crowd. i don't have a F-body anymore, but i still have many F-body friends. not to many people are running them on mustangs so it's really hard to say.
personally i would go with MPH i have heard excellent things about there stuff. VT has a good rep too.