Thanks SilverVH that information is what I needed. I wasn't aware that the big blowers like big turbos really spool up and kick in further up the rev range. Your comment about target power is a right on the money - I never looked at it that way but I suppose my question about usability is exactly this. I don't want to get too practical because on that basis the 6.0 with the current Walky Power upgrade already feels like I am carrying a cannon to a knife fight most times - in respect to everyday traffic. On this basis a smaller displacement blower would be better on public roads.... rather than generating big boost from a bigger blower that's mostly being bypassed - unless I get a chance to unleash (which I don't want to do on public roads). Looking at supercharger applications in factory cars and they're mostly used in cars that run smaller motors but need to deliver more power / torque. Given how taxes work in Europe (based on on engine displacement) I can see why Merc use Kompressors
Jag use them in the XJR for outright performance. The Eaton 230 is probably better for track work, but I am rarely going to go there. I think user dmacey is right, I need to get a chance to drive one of these things before laying down the money. I'll ask the walky sales guy for drive when Im ready.
In respect to warranty Walkinshaw have a very comprehensive warranty on driveline. It covers everything between the motor and the wheels. My experience to date given my current mods with Holden has been great. I had an issue with engine heating up a bit and thought Holden would just laugh at me and blame the Walkinshaw ECU. But thankfully no, they checked it out (dodgey cap on the radiator reservoir was losing pressure) and didnt utter a word about the Walky bits. I think given the Holden dealer is selling Walky accessories in the shop and the commercial relationship with Holden and HSV, the Walkinshaw mods are respected and not raised unless something directly related to running gear failure comes up..... at which time the Walkinshaw warranty would take over. For this reason and for resale value I think I'll stick to Walkinshaw. If the car was 5 years old I would not bother, I'd find any shop who know their stuff.