I didn't read this particular review but I bought the Interphone F4 "twin-pack" last week and installed it in both my Schubert S1 Pro and my girlfriends Shoei Raid II.
Biggest reason for buying was that we were going on a bike trip (we did it yesterday) with a few others - about 700km of driving on one day and we wanted to be able to talk. Luckily Hein Gericke (Flensburg, Germany) had 20% discount on everything so I saved quite a bit... the package arrived 3 days later and I had plenty of time to install and test.
First test was calling her via bluetooth connected phone while I was riding my FZ6. I was in between doing around 80-100 km/h and she could only hear my voice. She said it was almost like as if I was standing in a soundproof chamber... no "wind-noise"... only a few times from standstill she heard a slight bit of engine/exhaust sound but that was it
Before the above mentioned first bike-testride it took a while for me to fit everything in the Schubert S1 Pro. The whole internal mouth- and cheek structure is glued to the to the helmet (most likely for better soundproofing), so it took longer to figure out where to fit the little cables. Even though the speakers are very flat I think it was difficult to get a good fit, because there isn't much space between and around my relatively small ears and the "ear-spots" inside the helmet. But after about 10-15 times of "helmet on => helmet off => refit speakers" it felt good. Right after I found the right fit I sat at home with my helmet on to do some "off-road" testing... In standby mode there is of course no sound at all, but when calling someone (via bluetooth phone), listening to music (via bluetooth phone) or F4-F4 chat-connection there is a noticable constant static-sound. I just thought WTF and was quite unsatisfied... until I thought about that I would be unable to even hear this static sound when riding the bike... and this turned out to be correct!
Everything was easy to install in the Shoei helmet. Most internal structure of the helmet is just clicked on so took only a maximum of 10 minutes of fiddling and it was ready to go.
The trip...
I am not sure how close to the 10 hour limit of chat-time we were but we were able to talk during the whole biketrip. We only shut the connection off to standby mode during breaks at gasstations, breakfast on the ferry to Nothern Germany, lunch, dinner and so on. The system only cut the F4-F4 chatconnection once, but that was probably because my girlfriend accidently pressed the mode-button on the side mounted F4 reciever against my helmet when she was resting her head on my right shoulder... so all in all - the system never failed and worked for many hours!
All in all... Good clean signal... Even at the last 100km where we averaged 150km/t on the highway. On this last faster pace I used a pair of inexpensive "Alpine Plug & Go disposable earplugs" to kill a bit of the annoying wind noise and I just turned up the F4 volume to max and was still able to hear almost everything my girlfriend said.
I even came to think the above mentioned static sound was a good thing, because it indicated when the F4-F4 connection had been made just before we started riding after all the breakes. And even when riding slow through small towns we couldn't hear the static sound anyway.
The Interphone F4 really made this long trip so much better. It's not like we constantly talked but it was really really cool to just have than open two-way speak line to be able to comment on all the things we saw and and just chat in general. When riding 2 on one bike between 80-150km/t++ it's quite nice to be able to communicate. Things like "are you comfortable", "is the wind-pressure to hard at this speed", "you can go faster" and so on...
On the same trip I did a acceleration run from 50-220km/t at a long straight line of late evening highway with zero cars. With the F4-F4 I was able to hear her laughing the whole way up there. The manual says that the company promises a solid connection up to 180km/t, and I believe this. At the few seconds we travelled at 220km/t I couldn't hear excact words but I was still able to hear if she had fun or not... and she did...
I haven't tried any other similar products but I can still only recommend this for what we used it for.