Avoid it if you have held out for this long. As soon as you join and accept your friends, the likely result is that you will hear less from them, because they assume you've seen their updates in your news feed. They won't call you to tell you about a party they're having, they'll just post an event and expect that you'll get the invite.
I would really like to delete my profile and run away from the whole thing as fast as possible. I really don't like Mark Zuckerberg and his practices, not to mention the complete disregard for people's privacy, even profiting via selling your personal information to third parties. The only problem? If I did, I would likely never hear from a number of my friends ever again, neither would I have a means of contacting them reliably. I would probably also miss out on various parties and events. The very reason is simply by signalling to my friends that I have a Facebook profile, therefore no extra contact effort is required from them when mass communication suffices.
I agree totally with scruffypup that it's a false intimacy. In fact, you may find with friends you add that they become more distant with you.