I have a port-matched 3L. I ran 93 octane for the entire 2.5L SVT engine's life; then ran 2 tanks of 93 with the 3L and then switched to 87 octane for 5 or 6 tanks before switching back to 93. Although there was no detonation (knocking), when cold I would get a hesitation between 1500-2000 RPM at light throttle. Consistently. I see comments about the SVT computer and 19lb injectors being "tuned" for 93 octane; I don't know what the reasons are for my car having had that issue but after switching back to 93 it went away. I also noticed the engine being a little more responsive to 93 octane - and per my butt dyno, had more power too.
If you drive 15,000 miles / year, average 22 MPG, and assume 93 octane is $0.30 more than 87, then you're looking at $200 / year more. If gas is averaging $3.00 / gallon, that's less than 10% of the cost of the gas ($2,045). If gas is averaging $4.00 / gallon, then it's even less of an impact overall ($2,730). How many of us spend $200/year on stupid stuff for our cars, much less everyday life? I'm only showing the numbers to display overall the impact so you can make your own assessment if it's worth it to you. For some reason, we all are overly price sensitive on gas.