These two articles on the Vagina Monologues are worth checking out.
I agree with both authors about the Monologues - they are fun, they raise awareness, but there is also a bit too much essentialism in Ensler's approach to gender.
I first saw the play when I was a freshmen in college, and was blown away. It wasn't as if I had issues with my sexuality before this, but there were some things I definitely hadn't considered. As a result, I ended up buying a copy of the play and locating a hand mirror. (Another book that made me reconsider my approach to certain things was The Curse which I read sophomore year - after that, I never felt uncomfortable or awkward buying tampoons openly again or pulling them out of my bag - it's a natural function, dammit, deal with it. When I was at BOLC II, one of my roommates who was actually incredibly loud and outspoken about many topics was embarrassed to be seen carrying tampoons around a store so I ended up grabbing them - I wasn't about to get a cart for two items)
I saw it again my sophomore year, and then ended up too busy to go my junior year, though I almost auditioned. I even had one of the speeches ("The Vagina Workshop") memorized and "performed" (I'm not much of an actor) it sans the British accent at a Roe V. Wade anniversary event. I really wish I'd actually had the guts to go out of my comfort zone and audition instead of worrying about time conflicts with ROTC.
When I went to see it my senior year after spending the last two years focusing a lot more on my gender studies major, I had a slightly different reaction. I still liked it but many of the approaches seemed almost too simplistic. Other things seemed to support certain stereotypes about race and gender (for example, every production I'd seen had a black woman do "My Angry Vagina" - the black woman has to be angry? That's not the only thing I noticed at the time but it's been over two years). However, despite that the play is rather funny at times, sad at others, and is being used to help domestic violence victims.
The backlash from the conservatives is also entertaining- "oh my God, they used the word vagina!" Also, somehow, The Vagina Monologues are apparently responsible for a lack of chivalry causing a movement called "Take Back the Date" in response. Some people are just idiots.
* That's a quote from the monologue "Because He Liked to Look at It"