Hi folks, I bought the app and installed it last Friday. I paid the 30 Euro additional cost to get the ability to change to the US region. It all works perfectly. I'm really pleased with it. I wasn't fussed about doing a big change to the max speed but simply having another 3 mph makes a real difference. I used to get really frustrated with the motor assistance cutting in and out and just raising it a few mph has made a big real world change. I found the "anonymous Russian developer" to be really helpful when I emailed him too.
Linking to the bike took me a couple of attempts but now that I understand it I can connect everytime. (open app to connect screen, press start on the motor and as soon as it beeps/shows on the display click the app to pair).
Earlier last week I tried the E-max and I couldn't get it to pair. Given that I have just saved myself 100 Euro I'm pretty pleased.