Pros:
You don't have to worry about roommates always being around
You can eat everything in the fridge without worrying if it actually was yours or not
You can have your SO over with out worrying about who is going to care
You only have to clean when you want to
There's never an issue of "who's turn" it is to do something
Cons:
If you have never lived alone before, it can get kinda lonely
It's more expensive. Not just the rent, but remember that you have to pay for all utilities yourself.
If you don't have all the furnishings of an apartment, you have to go out and buy them.
There's no one to blame for the mess