4 stars: App is a little slow to load at times, but overall an essential (but not compulsory) companion for Sony headphones. It gives a whole range of options and firmware updates. Would be great if the app looks nicer. It kind of looks very unattractive and plain, imo. But it gets the job done (most of the time). Also please work on more accurate battery indicator. My indicator only goes 100%, 70% , and 30%. Thanks!
5 stars: The Sony XM4's are damn good! The key to getting great sound is by ensuring that you achieve a tight fit with the ear tips. To assist with that, Sony has included an app to help you get an optimal fit. Noise cancelation is top notch. There is also a convenient speak to chat feature that automatically stops the music when you speak. Call quality is excellent as is battery life.
3 stars: In general I like the personalization options of the app, but started to be really annoying when I started using it with two devices. I want to use Adaptive Sound Control in one only, but you can only turn it on or off for all your devices. Let's say, I want to go outside and listen to my surroundings if I'm walking, but I don't want that if I'm at the office and I decide to move a bit.
4 stars: Overall really good app. Controls are easy and intuitive. My only complaint is the equalizer. Somehow, each time I turn off my headphone and start listening again another day, the equalizer in the app will be swtich back to none so my previously saved equalizer is gone....