Never had a 520 but have not had any sensor drop out issues at all. The battery life has really been amazing which I am so happy about. The screen is also so easy to read and handles TR workouts and navigation with ease separately. Not sure if you can do both at the same time as I have not tested that.
Had a wahoo bolt (one and only non garmin product) that I enjoyed and like @miesemer above I sold it and got a 530 for the varia radar. Varia is killer and makes riding so much more enjoyable.
Thanks for the feedback. I had a bolt as well, and Varia pulled me back to the 520. For the most part I love it, but when I run radar, power, and hrm concurrently, I get constant drop outs 
That sucks for sure. Hopefully someone can chime in if they had the same problem with the 520 to help if you try to fix it before upgrading if that is the path you are possibly going.
Radar is coming to the Bolt - seems fairly close as it is already being tested.
That’s great news, do you have a source for that?
Shane Miller mentions it at end of the video
Seems alright thus far.
My issue with it (me) is I copied over a load of setting files from the 520 and seem to have made it difficult to connect my sensors - or at least for the UI to show their status. The data is there, but only the Bluetooth of the Stages PM is detected.
Guess it needs a reset.
With the latest firmware my 530 no longer has sensor drops outs, I also run power, HRM and radar, the battery life is awsome. I went from an 820 to the 530 and lts so much better IMO.
i have a 530 and I’ve been loving it so far. I had one glitch initially where it locked up and I had to reboot it, but it’s worked flawlessly outside of that one situation. No issues with sensors and navigation is awesome, really do love the turn by turn. I’ve had good luck with the outdoor workouts as well, can’t say the same for my own performance in said workouts! So far, highly recommend the 530
I had a Garmin Edge 830 for three months and got so frustrated with it that I took it back and exchanged it for a Wahoo Elemnt Roam. I had an Elemnt Bolt before and never had any problems with it. With the Garmin, I started having sensor dropouts and, over a period of weeks, the problem seemed to get worse. Having my heart rate monitor dropout intermittently during a really big hot summer ride is what really did it for me. Looking at Garmin’s forums, it’s obvious that they’re aware it’s a problem (for both the 530 and 830). Based on what I’m seeing, it looks like it might be an issue with BLE and, with Garmin’s track record, it could take months to fix. I didn’t want to take any chances so I bailed and got a Wahoo. It doesn’t have as many features but it does have a really nice clean design and, more importantly, it’s stable and works. Just my two cents. 
I’ve just upgraded from a 520 which gave me very very few problems.
So far LOVING the 530 - they fixed the biggest problem imo the 520 had: the slow laggy interface/CPU/processor. This thing is fast!
The mapping works so well. ClimbPro has been useful. I’ve not been able to get GroupTrack to work yet, it’s the only feature remaining that I’ve not had a chance to test.
Does anybody get WhatsApp msgs show up on their 530? They didn’t show on the 520 but do show on my 645 Forerunner from last year.
I tried out the Roam and then sent it back. For some reason they decided to save $1 of parts and only installed enough memory for have the map for one or two states at a time. Since I live and work in two different states I couldn’t even load both of those maps at once (since they are bigger states) so it required deleting and reloading the maps every time I went back and forth. And you have to have a wifi network to do it. Compared to Garmin, Stages, and everyone else having the entire country or more loaded at once. Seems incomprehensible to me for a unit that is supposed to be centered around navigation.
Just curious, is Garmin vs Wahoo reflective of non-Apple vs Apple? It’s pretty distinct in the crowd I run with.
It is (in part) a similar religious debate. I’d say more rational and pragmatic - people move from one camp to the other based on personal experience (mostly bad ones), they don’t excuse the Cult if they end up with a non-functional device.
That’s pretty interesting. I definitely see parallels-- the Wahoo is simple, maybe a little overpriced for its feature set, and seems to “just work”, while the Garmin is overcomplicated and maybe a little buggy, with poor interface design. I recently switched from Wahoo Elemnt Bolt (lost in forest during mtb race crash) to 530 (thought I should try the latest and greatest) and have to say, although I acknowledge that the Garmin is objectively “better”, I miss my Bolt! It did everything I needed without me having to think too much. I think in the long run I will appreciate the Garmin though. I’m a current Android and former Apple user.
I was pretty sure somebody had asked about whether the segment screen is based off where you are on the segment, or just the time progression.
Hadn’t tested it at the time, but pretty sure it is using position and elapsed time to compare with the leader and your previous times.
Did anybody else experience spontaneous reboots while using navigation?
Last Saturday it rebooted twice during a ride I had pre-loaded.
After the reboot it goes straight back to navigation although it needs to recalculate the route again and keeps all your data (i.e. distance, speed, HR etc.) you have built up so far on the ride.
I’ve used navigation loads of times before on it and never had problems before.
Haven’t had any spontaneous reboots while navigating.
But speaking of reboots, I decided to let mine update to 4.10 this morning. Now it is stuck in a bootloop that the power button won’t interrupt!
Edit/update: If anyone else has this problem, I was ultimately able to shut it off by holding the power and lap buttons at the same time. Then the bootloop was fixed by doing a reset: hold the lap and start buttons at the same time, press and release power button, then release power button once the logo appears.
I’ve had the 530 for a week and am keeping it. Overall its a nice upgrade from the 4+ year old 520, and in particular its really easy to change data fields while riding. There is one annoying bug with auto-upload after a ride, still present in latest 4.10.
Interested to see how well Training Status works, I’ll bet it works for some and not others. Yesterday received my first report and it said training was productive and I need more low aerobic work. Mind not blown, but it was accurate.