I've been using my 520 for over a month now. I had a Garmin 25 for the past 2 years. Wow, this thing has many more features than the 25. The amount of data is provides can be a bit overwhelming to an old dodger like myself. But after a few weeks I've come up the learning curve. It's nice that all the data screens are fully configurable. I'm using bluetooth to sync to my phone and finding the Garmin Android app to be much more useful than it was with the Garmin 25. It's easy to download routes to the 520 from the Garmin app on the phone. I can now configure my HR zones in Garmin, which the 25 didn't seem to support.The pros:1. Garmin Live track is very cool. My wife can now keep tabs on me during the ride.2. The accident detection feature is cool for the pedantic users. I actually triggered this on a rough MTB trail and my wife was notified.3. Amazing variety of metrics and support for various sensors: HR, cadence, power meter, etc.The cons:1. The gradient metric seems to lag. If your ride a lot of rollers, it may not be useful. It seems to work better on long grades.2. Haven't been able to find a way to configure the zoom level on the map. The auto zoom was too confusing to me, so I disabled it. The default zoom level is too low for me.3. The weather alert is annoying and needed to be disabled. If there's a thunderstorm in the area, it'll just keep alerting you every 5 minutes, which blocks all the other metrics on the screen until you clear the alert.