Personally I think people are being a bit harsh on procomp products. Even if they aren't the highest quality parts available, I do wonder how much grief they get because they are made in an Asian country, even by some people have probably never used the product.
There always seems to be a lot of "I've heard...". While some of this might be factual, there is so many causes that might be immediately dismissed/ignored when that part failed.
If you want the highest quality and performance, go pay for it. $629 for a pair of brand new complete aluminium heads sounds damn cheap to me and provides people with a low budget an 'option'. No one is forcing you to buy the cheapest part around. The company has likely had to make sacrifices in quality to achieve such a low price and you should probably expect that.
I'm sure there's people selling products like this who advertise it as something it might not be, but I believe Skip gives a pretty honest description.
What I've written is my view, I'm not saying they are good or bad I just don't believe 100% of the criticism against their products is called for.