Those heads work pretty good on a mild street build. The major problem has been that they were so expensive that you could buy a used set of Thunderstorms, XB's, or late model heads and have them professionally ported for less money and the worked over stuff would out perform them.
Recently it has been possible to buy these for greatly reduced prices and the price of new 04 heads has gone up so they look increasingly attractive if you are going to just buy them off the rack and install them. ( I would still rather have the oem heads)
One potential problem is that Edelbrock did not move enough of these things for obvious reasons and they are clearing their inventory and will no longer support them. They have a special flange in the intake area so they require their intake manifolds which also require their manifold gaskets. I see this as a pretty big potential problem since they will no longer be supporting this line.