It depends on what you want from it.
If you want to be able to compare segment times against those you follow, or by age group, or clubs, or weight range, then you can only do so with premium nowadays.
It also gives you the "live segments" option, where segments you star will be synched to your device which will then show how you are doing against your PB (or against the KOM/QOM if you choose) while you are actually riding the segment. This does depend on your device having that ability as well though - not all do.
It gives much more analysis of your training and effort.
It gives you the ability to plan routes (though there are plenty of free apps which will also do that) and transfer them to your bike computer.
If you have the mobile app, that will also let you generate loop type routes of a given length, and hillyness.
I subscribve, and personally find it worthwhile. But it is very much an individual thing, and I can't say whether it would be worthwhile for you.