At the beginning I was concerned with the battery performance but after using the radar in the blinking mode all my concerns went away. I have used this product on a 7 hour rides and it has worked great. You just need to be sure to use it in the blinking mode if not the battery last around 4 hours.
Paired with my Edge 520, this rear light alerts me when cars are approaching by showing RED highlights on both the left and right edges of the screen. Even better, on the right edge of the screen inside the RED highlight is a dot for each vehicle that is approaching you. Each dot starts at the bottom of the screen and slides up the screen as the vehicle is approaching you (moving up the screen faster if the vehicle is moving faster). Once all the vehicles have gone by, the left and right sides of the screen flash GREEN to let you know the cars have gone by. It feels so much safer riding on the road to know that a car is coming so that you can time your look back accordingly.
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.
These lights are inexpensive, work well, are light, low profile. Not quite suitable for dark trails at night but general commuting or riding urban areas during low light times they're great. The various ways to attach the light are super convenient. Great product.