That's extremely pricey. With an uprated fuel pump you shouldn't need a seperate pump for fuel, that should be governed by the solenoids fed from a T off the fuel line.
If you're giving it a 100bhp fixed hit in a fairly standard car then you'll probably lose traction, not to mention most of your engine internals.
Nitrous is just like any other power-enhancing mod for cars - it takes knowledge and proper tuning to do it properly. After all, would you just bolt a single kit to your Supra and hoon around without getting it properly tuned?
If anyone is serious about nitrous, then I can't recommend the Wizards of Nos board enough.
:edit: Re-fills depend on the power you're using - expect 10-15+ minutes of continuous use on a 50 shot with an 11Ib bottle. For 2-3 minutes you'd have to be putting in some serious amount of nitrous!
:edit 2: Dammit! All this nitrous talk has made me make up my mind to put it on the TT! You evil people!
:edit 3: Progressive controllers are to minimise the effects of a sudden hit of nitrous - if it helps, think of it a bit like impact loading (getting past my techie threshold here!) They also save your traction either off the line or whilst moving. Ideally you should go progressive on anything 50bhp or over.