There are lots of 'symptoms' that are great about being an entrepreneur, but I think they are all a result of Self-Actualization (and maybe Self-Transcendence) from Maslow's Hierarchy of Needs: http://en.wikipedia.org/wiki/Maslow's_hierarchy_of_needs
For me, this manifests as:
* Creating change for the world outside of personal gain.
* Learning the limits of what I can and can't do. Nothing like jumping in the deep end to learn how to swim.
* Getting fulfillment that I wouldn't get elsewhere. E.g. amazing people, satisfaction in work, creativity, and bringing meaning where there would be none.
There are some commonly cited but wrong answers. It's highly unlikely you "have no boss" as an entrepreneur (fiduciary responsibility to shareholders). You don't get to do whatever you want. You don't get to slack off and take vacations.
There's also the "E-Myth" - if you like baking pies, don't open a pie bakery, because you'll spend barely any time making pies and you might come to hate it.
I believe some people are meant to be entrepreneurs. In other words, just like how you don't choose to be gay, you don't choose to be an entrepreneur. So the best thing about having an entrepreneurial job is that it lets you be who you truly are.
... or as I put in some of my social profiles: "I learn by pushing boundaries until something pushes back. So I landed in one of the few jobs that rewards such silly behavior ;)"