*Very* important to do this, in my opinion. If there are "fun things" even if just like a rented movie and popcorn on a Saturday night, it makes it a lot easier to keep with a program to get out of debt. As soon as it goes to "we can't afford that $5 movie rental" things suddenly get a lot more tense.
It all depends on what you want to put the money into. I try not to go the theater too much though just because if you're going as a couple it gets very expensive very quickly and the enjoyment is gone after just two hours tops. They are great at ripping you off there.