is it worth it?

I'll try to be objective.

The Pros:

1. Graphene gives you more "control" over your data "out of the box" than any other custom firmware. Yes, you can patch and mod your favorite firmware to your liking, but graphene "just works"
2. It's rock solid and reliable. It only supports one hardware family. I've never had graphene lock-up, crash, camera stop working, etc
3. The installation and upgrading is amazingly easy (compared to other cfw) and streamlined. After the initial setup, it behaves just like any ofw.
4. You'll see just how much of an intrusive cancer Google has become (Google play has a "feature" where they'll dynamically load code and try to run it - graphene blocks this kinda crap).
5. Going back to stock Google (with locked bootloader) is rather easy. So you don't have much to lose (other than a few hours) in trying.

The Cons:

1. Some apps will crash. Graphene hardens how applications behave (in terms of accessing memory, for example) some apps are buggy and will not work. Not many apps (may 1 or 2 out of 30+) but it does happen and you can fittle with the app settings to try to fix it, but it's tedious through trial-and-error
2. Some apps won't work, like maybe your bank because it will never pass the "Google integrity" checks. The fear and concern is that more and more apps will start to block cfw. So expect that you might need a second device.
3. Any apps/processes that deal with money (tap-to-pay, Google wallet) probably will not work (again, it fails the "Google integrity" checks).
4. (personal preference) I don't like the graphene launcher nor their store nor their (boring) default icons. However, graphene empowers you to change/replace all this.