++1 on Uncle Phil's posts above.......
I had the Rostra on for two years :
Yes, it worked, but never was right. OK on level ground, or uphill, but surged everytime it engaged, going down hills, and was just generally unusable.
After wasting $$ and a LOTS of time (plastic on/off, on/off, etc. to try different settings) with my Rostra, I bought the MCCruise.
My advice - spend the money. As Phil said, everything's included, you don't have to hack your wiring, and most importantly you don't have to jury-rig your throttles.
The more I thought about that arm down there, under the airbox, the more I worried that one day it might snag and jam up.
The MCCruise guys have put an incredible lot of work into making this specific to the ST. That's why it ain't cheap.
Very detailed instructions, wires cut and connectorized to fit and just drop in - the install goes very smoothly.
And, as has been said, they are right there for you if you run into a snag.
This makes the (approx) $800 I spent on this very well worth it IMHO.
Don't forget, your time is worth something also.