LinkedIn is great for networking, i just signed up a little while ago, some of my colleagues are pretty savvy and use it to their advantage. They also have a lot of users, so yes, it's great, use it, you'll like it
LinkedIn has been very nice for me because I get connection requests from people I lost track of more than a decade ago. You can find me on LinkedIn at Will Spencer.
It's wonderful.... Everyone I've found on there.. that I've met in my life.. I like... That's rare online
For me it is worth to have a profile on linkedin. I am doing alot of networking at that is important in todays business
LinkedIn is pretty good to advertise yourself for business. Here is mine aswell http://www.linkedin.com/in/eddywuchaney