Ok so it's for sale.. I installed it last August (very easy install) and have only used it for Autox's, a couple trackdays and Knox, no daily driving.
Never had any problems with it, this thing is awesome and you can make easy power with it up to the 220-230 range with simply bigger injectors, intercooler, and some type of fuel/engine management.
Here is a link to 949's site so you can read up on it.
http://949racing.com/rotrexmiatasupercharger.aspx
Price is $2700obo - this is the complete kit that is about $3600 after tax.
Remember just the supercharger alone is $2650usd!!
I believe the kit can be retrofitted to fit other years of miatas...