The 645M is one of the best watches at its formfactor.
I might offend someone but here it goes.
Personally I CAN do the following with, contrary to common knowledge with the watch.
- Check HRV
- Check Body battery
- Quick PacePro
- Offline map datafield in color with a heading arrow superimposed
I admit workarounds but I have only used garmin for a few months only.
Great little bugger