1) I had my 9500i in Pilot Speed mode today.
The speed display worked fine on the way to a restaurant this afternoon and then my parents' place.
However, tonight when I started to drive back home, the display was initially stuck at "0 MPH".
I unplugged it and plugged it back in and also tried playing with the programming.
After 6 or 7 minutes it started working again by itself.
I think it dropped to 0 MPH for just 1 or 2 seconds two times after that.
Then it was fine for the last 15 minutes of my trip.
I don't know how the speed measuring technology works, so it may be something that happens once in a while.
I has the GPS filter off the whole time if it matters. I did, at one point, turn GPS on and back off.
2) How accurate is the speed display?
The 9500i's vehicle speed display seems to always be ~ 3 MPH higher than my speedometer...
I don't know which to trust.