I started using the 520 on August 8. I did 30 rides so far and on 3 occasion the unit went crazy. Yesterday was a good example, on a 50km ride, it reset itself 3 times and froze 5 times. The only common data with these 3 rides was the cold temperature (<10 Celsius). I installed the 3.00 update yesterday evening after my ride. I hope it will fix the issue because when it starts, the unit is useless.

I notice also that live Segment isn't very accurate. I went full throttle on a local segment and my time was 1:23 placing me in 7th position in my mind. To my surprise, when I upload my ride, my time was 1:19 and I jumped in 2nd place. So I learned not to give up too early when the 520 tells me I'm behind my target time in a segment.

So far you can't customize the screen layout when a segment prompts. Therefore you lose all the basic information (Watts, HR, Cadence) much needed to monitor your performance and do good in the segment. The screen shows the name and time of your target. A useless map of the segment, the distance remaining in the segment and your current time compared with target (seconds behind/ahead of target).

On the Bluetooth side, its paired with a Samsung Galaxy S3 and worked flawlessly from day 1. I can upload my ride in less than 10 seconds every time without touching my phone. I just need to log on my account from PC or Phone to rename the ride if I want.

Pairing with ANT+ devices is working very well also. I run a Stages Power Meter and it never failed to connect. Same with my HRM, everything is perfect. I don't have a Speed/Cadence sensor because cadence data is provided by the power meter. No issue there.