Ive got one (from the first group buy) and installed it a couple of days ago; absolutely painless installation, I'm not known for my mechanical prowess and had no problems.
Not sure if it has made any difference other than removing the speed limiter, prior to the gipro the bike would start to run out of puff from 160kmh but now just keeps pulling.
Wrt better acceleration it could be as some have stated if you have the TORS tune (which I have) it closes the secondaries further than the standard tune; might try going back to the standard tune to see if it makes any difference.
Peter