Ditto. LinkedIn is a self-updating Rolodex for me and it's useful for that. Plaxo sure wasn't any better and I do like having a service of this basic type.

I basically don't use it for anything else and generally ignore emails that they send me. (And only accept connection requests from those who I--within 5 seconds or so--see some reason to connect with. If I don't recognize your name or your company doesn't imply some good reason to connect, I'm ignoring you if you send me a canned request.)