The most convenient feature is that it does not require any extra equipment or software to be installed, so no need of installing anything in my phone! It gives me accurate data about where exactly do I have visitors' attention while using an application/website by simply recording their gaze direction with its camera (it can also use front-facing cameras).
There's nothing bad from this tool as far as we know; everything seems fine - maybe just some minor bugs here & there which could get fixed soon if they're reported properly via app store reviews? We've been solving issues like user retention through our products since last 3 years now but never thought before how much people actually look into them once open up!