The Fluidampr crank pulley looks like a great reliability upgrade but after searching the site it doesn't seem to be very popular. I can only find a couple of posts where people event mention the Fluidampr on the LS1!

Is it all hype or do people not want to spend $350 to help their engines?

 

I doubt it is worth the trouble. I think they have an underdrive, but it is only 10% or something. I have the fluid dampened March pulley. It is very nice, no problems during the install (other than it being particularly snug). I am very pleased with it, and I have never heard anything bad about it.