I have been using the earlier version of Varia Radar 2 for a bit over two years. I have been told by drivers, among them two FedEX drivers, that it is the most effective tail light they have ever seen. It was visible at a distance of more than a mile. It begins flashing as soon as a car comes within the radar range. I ride just about every day and I have never been surprised by a vehicle coming up behind me. My computer beeps and the display of the vehicle or vehicles approaching shows along the right side of my Edge 1030. I can judge the speed and distance of the approaching vehicle from the display. It really is a remarkable piece of equipment, and it sounds like they have made it even better. My unit will start giving me a low battery warning after about 4 hours on a ride. I have never run out of battery, but my rides don't usually last longer than 4 hours. The longer life battery is certainly not a waste. To give some idea of the sensitivity of the radar, I was once standing by the side of the road taking a break when a runner I had passed earlier approached. The computer beeped, and the display showed the runner approaching. That is pretty amazing. Yet, at the same time, when I have ridden with another rider, his presence is not noticed by the radar, only cars approaching us. The stimulus for the radar is something approaching, not something keeping pace with you. Recharge time is about an hour or less. It is, in my opinion, a necessity if you ride on the road. It will pair with most Edge computers and, also, with Wahoo computers.
The Edge 530 has been a great addition to my cycling. With the integration w Garmin Connect, its very easy to create training workouts, custom routes, and also more detailed performance stats from each of my rides. I've used it for both road, gravel, and mountain biking and its well suited for each discipline. The battery life is solid. I've only done 1 longer (5 hours) ride with it, but had no concerns of it dying somewhere along the way. Normally, I use it for several 60-90 minute rides a week and typically only charge it once every other week. It integrates seamlessly with all of my sensors (garmin speed and cadence), heart rate strap (garmin chest strap), and lights (garmin varia headlight, garmin varia radar). It has changed my cycling experience. The only reason I didn't give it 5 stars is that periodically there are some small annoyances like auto downloads restarting your ride, but these are few and far between.
Well most head units are Garmin and use ANT, and then Ive got a TACX Neo2 (which Garmin recently bought TACX) which uses Bluetooth with my Apple TV. So if you get this heart rate strap your pretty set as it work seamlessly with both the Garmin headunits ANT and Bluetooth as needed. Plus its comfortable and I like the strap.