I use all three shades of Alclad's Primer & Microfiller with great results. It's easy to spray right out of the bottle, sands well and takes finish coats well. My finishes tend to be Tamiya acrylics or Model Master enamels, and I get good adhesion with both. The P&M products are also a good choice under their own metallic shades, which work very well for me.
I think what Black Sheep is referring to is Alclad Gloss Black Base, which had some bad batches that resulted in poor drying and were not at all satisfactory. It is recommended as a base coat under the high shine metallics, specifically Chrome. Several people have found that Testors Gloss Black is a good substitute. The unfortunate reputation that came from the "bad batch" scares a lot of folks away from their products even now.