Joi Ito's Web: LinkedIn launches! hosts a lively discussion about the new LinkedIn service, with contributions from founder Reid Hoffman.
I have responded to an invite to join up and am in the process of inviting some of my own network, so judgement is reserved for the time being.

is it much like the old six degrees site (linked associations based on personal connections such as 'friends', 'relatives' etc)?
http://web.archive.org/web/19991116034501/http://www.sixdegrees.com/