Welcome to the DIS!
"Worth it" in terms of what? It's too hard to answer that without some more information:
- Will you be bringing your own camera? If so, cast members can take photos with your camera.
- Are attraction photos of interest to you? If so, those are included with Memory Maker.
- Will you be doing character photos?
- There are special "magic shots" that include digital graphics superimposed on top of them. Do a Google search to find them.
Basically, it comes down to a lot of factors. Take a look at the products page here and do the math to see how many photos you'd need to buy on your own to break even, then weigh it against your priorities:
https://mydisneyphotopass.disney.go.com/keepsakes/index/notlogged/