While this firmware is still relatively new, my initial impressions are "thank you, Garmin!".
The update seems to fix one of my annoyances with the device. Namely, the crappy elevation data it would produce. I've noticed huge elevation differences between Garmin Connect and Strava. After the update, the unadjusted garmin data is mapping very closely to the elevation adjusted Strava data. That is refreshing to see.
Garmin: Edge 510 Updates & Downloads
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Thread: Edge 510 2.50 firmware