I bought the Garmin 45S on Black Friday, after umming and ahhing for some while. I have to say having the smart watch is motivating me to get out for a run twice a week (I had faded to maybe once a week). I found it fairly easy to get to grips with, although I haven't changed any default settings. I simply downloaded the app to my phone and the watch syncs straight to the phone so it is very easy to check up on my activity at the end of each day. One very useful feature, I set it to prompt me to move after being still for an hour (usually sat staring at my laptop).
One surprise was finding out how much I actually sleep (more than I thought, as I often find myself awake through the night).
A second surprise was my VO2max score (I had to look up what it meant)