It's both fun and hard, and you'll quickly swing from loving it to hating it and back during each shift.
Its good experience though, and it pays decently, so it's worth trying it. And if you end up hating it, quit.
Well yes. It does have it's upsides.
You get a lot of social training, you get to work on your flirting abilities (:P) and sometimes you get the ladies.
But another negative thing is that you easily become an alcoholic... sorta.
At least where I worked we stayed past closing time every night to drink, a lot. And that became a habbit. If you worked the day shift you stuck around afterwards and had a few drinks (enough to make you tipsy) just to relax as working as a bartender is stressfull.
I didn't get used to it to the point of no return. As soon as I quit I didn't have a drinking problem, but when I did I drank a lot. Just something to watch out foor.