The Bionx 500DV I purchased in September 2015. In April 2016 it developed what sounded to me like a "cat growel" as I was ascending our local mountain. I took it into the dealer where I purchased it (Vancouver BC). The mechanic first checked for wheel/disc brake rubbing but confirmrd the problem was within the motor. Bionx had a replacement motor shipped Shipped to the shop which arrived within a week as promised. Meanwhile I continued to ride with the noisy motor as it operated normally otherwise.
In late May 2016 while descending a steep hill with maximum regeneration, a severe growling sound came from the motor area. It seemed like the same problem. However in the process of removing the wheel I discovered that the rear disc brake was somehow jammed. After servicing the brake, everything returned to normal. The dealer was also much relieved that it was not a motor problem.
As I ride in mountainous terrain, I have set the regenerative braking assist to maximum (40) in the console menu. On the DV500, this braking effect is amazingly strong when the battery is at say half charge, and usually causes the motor to shudder but is very helpful in reducing break pad wear. With the 555 Wh 48V battery powering the D500 motor I was able to ascend a local mountain (1000 m elevation) with 55% charge remaing and 100% displayed before reaching the bottom. On the descent I found that the braking regen was actually slowing me down too much (it would require me to pedal) so mostly I used the controller variable regen going down to better control my speed of descent.
I'm in my 11th year riding a Bionx electric assist road bike (currently installed on my 8 year old Devinci Oslo) and especially like that it has not only good power going up hills but great regenerative braking. I was pleasantly surprised how much more effective the regeneration is on the DV500 compared to my previous 250 W system as this was not particularly advertised. Well done Bionx!