I've never had any problems shifting using Bel Rey, ever.
The only argument I've ever heard FOR running ATF is that oils like Klotz, Bel Rey, MTL, and others like it are too expensive at 10 to 13 bucks a quart and ATF is 2.50 a quart at any autoparts store.
Doesn't that at least sound like being cheap? If we're are wrong, then educate us on why ATF is a better choice other than "its waaay cheaper".
-Ryan