New user here. I have a 7520 on Nextel and I purchsed the 810,820 and BT 250 and have experiemented with all three for about a week.

Athough I like the look of the 810 and 820, the overall sound quality was poor. Inside i got a significant echo at times and outside it was often inaudible on the other end. The echo continued even when i turned the volume down, although it was significantly less.

The BT250 surprised me and worked reasonbly well. In my office and in the car it works great. The only times I have problems is outside in wind and when I am in a wifi environment.

Although it is not perfect, the 250 will have to do for now and the 810 and 820 are going back.

Has anyone here had a good expereince with the 850 and the 7520? Since the 810 didn't work for me I am assuming I should expect similar results from the 850?