Spain to Germany
In my perspective, SafeSky is a fantastic app (I have only had a ULM Pilot License for two years and a few hours of flight time).
It ought to be considered a "MUST HAVE" tool, along with others... such as SkyDemon and Windy (for example this are the ones I use the most).
But we shouldn't forget to look outside the plane.
Several times, I was able to localize, follow, and advise my fellow pilots in formation about the traffic situation at any given time.
I highly recommend it as a tool!!