I've started to use Here Drive+ on my way to work to estimate my commute time. I haven't lost GPS signal like I often did with my Lumia 920, but I did notice some issues tracking my runs over the weekend.
On Saturday, I did 2 laps at a 1.5 mile track, and MapMyRun recorded that I did 3.34 miles instead of 3. Yesterday, I ran on city streets near my house. The app using my phone's GPS recorded as 10.62 miles. I used MapMyRun's website to manually plot the route that I ran, and it was only 9.77 miles. There seems to be about a 9% variance because the GPS is tracking me zigzagging as I run. It's close, but I'm not sure what the margin of error is supposed to be. It's not as accurate as my Microsoft Band (which is currently in for warranty exchange) has been.