I'm very pleased with it. I've had it out on a few trips now and find I'd rather check my vehicle speed on the Garmin than my speedometer. It's digital and very accurate. Bonus is that I can also see elevation, which is handy when heading to a trailhead. Normally I can tell how close I am by time or distance, but elevation is a handy alternative. And the fact that I'm charging the inReach all along is important too, of course.
Loses 1 star because the shipping was delayed by a few days until I pointed it out. More importantly, I found the attachment of the Garmin connector to the main support wasn't very solid. An easy fix was to put a bit of metal strapping on the backside, but that also loses a star.
Otherwise I'd highly recommend it!