What field are you all working in that it's helped you so much?
I haven't found much luck with my linkedin profile, but I definitely haven't put as much effort into it as I could have - I haven't listed any of my published papers, no letters of rec or anything and it's basically just a detailed resume, and I haven't networked with any new people in my field through it, aided by the fact that the message boards for my company and alma mater are either filled with spam or vacant from conversations. I've had a few recruiters contact me, but mainly from those who are obviously doing shot-in-the-dark approaches to trying to find people with any amount of specific experience.
Once my part-time employees started "connecting" to me on there and vouching for my skills, I felt like it wasn't as professional as it originally appeared - I don't need a college freshman who worked for me telling employers that I'm good at data analysis. I've had better luck with people finding and contacting me by posting my resume on monster and careerbuilder.