I run with my Garmin Forerunner 205 all the time.
I had tried Endomondo on my Blackberry before but my battery was always drained by the time I finished a long run. Absolutely love the Garmin for keeping me on track and for mapping all my training.
Left my Garmin at home today by accident and downloaded MapMyRun for my lunchtime run - it seems to have done a fairly accurate job of tracking and mapping the run, but I was really struggling to see my current pace whilst running. Running with my phone in my hand also didn't feel right.
Alright as a back up but nowhere near as good as the Garmin, and if it was a "comfortable" run, not bothering about current pace etc. it would have been fine. I love the ability to track intervals sessions on the Garmin too - I don't think that's possible on the MapMyRun app.