Garmin has to be swapped from bike to bike, charged, switched on in advance (once outdoors) to allow time for satellite acquisition, remember to press start to record ride and save once finished, removed from bike if left anywhere less secure than Fort Knox and can be a bit flakey on distance accuracy if signal strength is compromised.
I only really got mine to use for navigation purposes in unknown areas, otherwise wouldn't have bothered as the traditional wheel sensor bike computer is stupidly simple, very reliable and might need a new battery once a year.