I Love My Garmin

 For things like keeping time when I run and figuring out things like VO2max, it's great!

But for distance, I trust it not.  Here's why. Take a look at what it thought I ran today:

 

Here's what my mapping app says I ran:

True, the mapping app has me running in the middle of the road, but that's only about 10 feet from where I really ran.  The Garmin app has me sometimes 50-100 feet off the road and constantly has me cutting corners in a way which would necessitate passing, like some kind of shade, through buildings.