Aint just as simple as strapping one on mate.
I've looked into this at length. Its perfectly feasible to install one, ideally in place of the air con pump on my hgt.
If I were to subject my mule to this ordeal, I would take the bhp up to 230bhp. If I ever wanted more than this (and I rather doubt I would, I could risk running it up to its max 14lb and potentially 280-300bhp).
You couldn't do this with your stock ECU or even a Dastek though.
If I had five years no claims and was debt free, I might consider a supercharger this summer. As it is I will not be able to afford to do it for at least two years, and I'm so fed up of my car being in the garage, I doubt very much I ever will.
It would envolve replacment of my stock ECU and dastek piggyback with a stand alone management system and I would need to replace many of my internals too. The Rotrex Supercharger would cost 1400, parts - forged pistons etc prob another 1500 + 800 for the new ECU and labour prob 1500+ with all the mapping. I would only trust Barbz at Torque Italia in London to carry out the work.