Yes I'm not only in Facebook to stay in touch with friends and family, but I'm also an avid LinkedIn user. (Profile here).
I like LinkedIn because it's a way to make and keep business contacts for a variety of reasons. I am, after all, a social-butter-networking-fly. :)
Its job board could stand to be improved, particularly when most of the results come from a third party vendor, but this is more a fault of not enough companies using it as a job posting medium. If CareerBuilder had an API that LinkedIn could use, that would be much better.
The site has been trying to promote the Answer community for a few months now, and it's pretty decent... much like Yahoo! Answers. But again, no blockbuster here.
HOWEVER, a hidden gem is the Companies link that proivdes the ability to research potential custmers, prosepective employers, etc.

On your home page, under the LinkedIn graphic, there are 4 drop-downs: People, Jobs, Answers, and Companies. Click the down-arrown next to Companies and select "Company Search"
I selected my employer, Siemens, and noticed different sub-headings I can look at: Career Path (jobs people came from and where they went after), Employees on LinkedIn, New Hires, Recent Promotions & Changes, Popular Profiles, Key Statistics and Jobs.
I wonder if a Popular Profile will soon see a Recent Promotion? :)
Given most, if not all, of this information is compiled from the employee LinkedIn profiles, there is something to be said about the veracity of the data . I wonder what the corporate profile of Microsoft or Yahoo would look like if summarized from the organic expression of its employees?
Would a corporation truly look like the sum of its parts? It would be nice to see some synergiztic effect realized beyond the scope of PR, Marketing and Communications.
Random Example... Hmmm... let's see... New Hire Don LaFerriere, VP, M&A, Bus Dev was SVP, Commercial Segment, at GE Capital 3 months ago. Commercial Segment = Business Development. I can see the logic. Continuing, it makes sense given GE is a "before" company. I guess when Don is ready to move on, we can bet that IBM or Microsoft will be an "after" company. Maybe Google's new VC arm? (In the interest of full disclosure, I have no idea who Don is and am hypothesizing based solely on personal interpretation of the presented data.)
Anyway, play around with it, and see what you think, but use at your own risk. I think I just modified the corporate information for a 160 year old company. DOH!