OK.. My observations on this.
Yes, there is a noticable 'whine' under load, but the thing is quiet when rolling down the level road without your foot in it. One HUGE change is that the down shifting is greatly improved. What I mean is that it does not seem like the rig is shifting from Overdrive to 1st gear when pulling a big hill or when you punch it to pass.
91 Octane or higher is recommended. Allen @ Nelson Performance can build a program that will allow the use of 87 Octane, but at the sacrafice of a bit of power.. (and of course some additional $$$)
http://nelsonperformance.com/
The H2 is DEFINITELY a different rig once this SC is installed.. and quite robust when pulling trailers or long steep mountain passes. Mine can hold 85-95MPH when headed up the Eisenhour tunnel approach (6-7% grade) here in Colorado with very little effort (except watching out for those tiny cars that seem to think it is ok to pull out in front of a fast moving Large vehicle).
The Magnacharger install is very clean and nothing is 'rigged' when the install is complete. The only drawback that I have experienced is that the new Oil filler neck is shorter than the original which makes it hard to pour oil into the engine without a funnel.
Hope this is helpful.
Oh.. one last thing. I have a magnacharger and a friend of mine also has a magnacharger. My MPG went down from 12-14mpg to 9-11mpg. My friend has yet to see anything above 9.5mpg (but of course you tend to put your foot in it a bit more with the Supercharger).