I've been using Amsoil since 1999 and switched to their Dominator 5w-20 race oil when they came out with it a few years ago. Lots of zinc and have seen excellent wear characteristics. They have a variety of other viscosities to fit most needs.
No dyno comparisons yet, but I've had to turn down the idle a bit after draining a conventional break-in oil and adding their race synthetic.
The college I work at is getting an engine dyno this year. Hopefully I'll be able to have them do some comparisons as well as tuning.
http://www.amsoil.com/techservicesbu...t%20Tappet.pdf