To go union or not...??

Well I got my first job, yeah me!! Durring the interview when it was my turn to ask questions (and thanks to allnurses I had some good ones!:wink2 I asked about Unions.
They told me the hospital was a non closed union.... I have never had any experience with unions, none of my clinicals were at hospitals with them.. so I have no idea about them..
I asked what the percent of nurses unionized were, they told me they had no idea, they only know your union if your an officer, but that they did know the union wanted to increase its members..
Any way I guess my question would be What are the pros and cons of being union or non union in a open union hospital??
**Sorry for the ramble.. still flying high that I am finally employed!!!**
Thanks all!
Congrats on the job! Here's an entire forum devoted to Union discussions: http://allnurses.com/forums/f323/Best of luck to you!