After doing a bit of research I decided upgrade from my 510 to the 520. I knew it was going to be a mixed bag - losing the touch screen, which I like on the 510, but picking up the Strava Segment integration and much sharper display. Well, it's going back tomorrow after one ride. I never got to the Strava features, the display was as reported, and everything else was a disaster:

- The interface is totally nonintuitive and the presence of six buttons and trying to decide which one to press to get to where you're trying to go or to select something makes it downright painful. It can take several keypresses involving several buttons to do what you can accomplish with two touchscreen presses on the 510.

- It seems to DRASTICALLY under-calculate total elevation gain. Today on a course I ride regularly with others, it reported 20% less ascent than my 510, with the 510 being consistent with what other guys I ride with report for the same course, using a variety of devices. It was easy to see why: on relatively short, modest inclines it registered little or no elevation gain, and even when it registered anything there was a delay. I've seen this reported by others; the consensus seems to be it lacks sensitivity and thus misses elevation that isn't either prolonged or dramatic - has to be one or the other.

- You can display average speed, but not average MOVING speed. The manual makes clear that it counts auto-pause time as elapsed time. It still calculates average moving speed, and you'll see it when you upload your rides to the Garmin website or Strava, but that's not what you see on the display while you're riding.

I absolutely HATE the thing, and that's after allowing for the bugginess of the 510. Yeah, the 510 can be buggy - mostly in getting rides to upload - but it's intuitive and accurate and won't drive you to suicide trying to set it up and customize it.

I've already re-boxed the 520 and have my Amazon return label for a refund.