I bought this as the group I ride with wanted me to be able to communicate, and I also wanted to be able to hear map instructions, online broadcasts, phone calls.

The group leader has a SENA 20. It took us a half an hour to pair up the M3 with the Sena. The only way is exactly the way the instructions describe it, which is roundabout and not like other systems. Basically, you have to treat the SENA system as another mobile phone, and pair with it. There are limitations then , not true intercom for multiple riders (unless they all have the M3!)

PROS:
packaging, appearance, contents, instructions all good to excellent. Good build quality.
Camera works as described, and a plus is that you can take still shots while video is being shot. Significant 'fish eye' effect - see picture
I took phone calls easily and the people on the other end of the line did not complain about road noise, even when I was on the highway at 60mph
Includes two mikes, a boom type and a button type
Battery life seems to be very good, Rode 4 hours with it yesterday, recording video and talking, no problem
Although he could hear my engine noise, the other rider said the audio was a significant improvement over just a headset connected through the phone.

CONS
The app to view video on the iphone without off loading the files does not work. Waste of time.
No Instructions are given as to how to position the device on the helmet for video. I spent a long time trying to get it right and still ended up with the camera pointed in a slightly off angle.
Speaker volume- max speaker volume could be louder and volume between apps is not consistent. For example, Audio instructions/confirmations from the system are lower volume than pairing conversation or map instructions.
Does not seem to have an option to record the paired conversation as part of the video without the road noise. This is a feature on some other brands.
Either the instructions are slightly off, or procedures not intuitive, but device is very sensitive to the steps you take to turn stuff on and then it is hard to know how to back out, shut down, or exactly where you are in the process.

If you are riding solo or 2 up and you both have the M2 this is extremely great value for money!

If riding with a group of cyclists with mixed headsets, be prepared to take some time to set it up.