Like the size, battery life, and menu selections, especially the ride history. However for the senior rider who needs reading glasses but doesn't like riding with them, the smaller display can be difficult to read.
As far as features, accuracy and screen sharpness this unit is definitely a step up from old Edge 500 - and in a slightly smaller form factor.
The one big drawback is battery life. Garmin claims 15 hours, but I could only see possibly getting near that if you have no speedcadenceHRM linked to it, no BT phone connection and using GPS only (no Glonass or Galileo). In addition, cold weather severely reduces the battery life - normally I'm able to get 8 hours of uptime, but when the tempurature goes down to at or near freezing, my unit consistently dies after 2.5 hours.