Been using it almost exclusively for over three years. There might be a 1/10 second differential in the 0-60 & a couple in the quarter mile, and a few missing MPH off the VERY top end, but my experience has always been that the mileage is the same (or better!?), my car always starts, runs great & idles smooooth!
I've never had any work done on any part of the ignition/fuel injection system except replacing fuel & air filters, the PCV (once) and plugs. A can of FI cleaner every 6 months.
If you can run at 140+ mph often, involved in lots of street races, 0-60 and @ the strip, or are highly modified, premium gas probably makes a difference, but a very small one. If you are like the rest of the SVX owners out there, IMHO premium is a waste.
Enjoy the extra dime (or two!) per gallon you save!