Not for me...
I don't like the idea that someone with access to one of the sites that the SSO system is used on being able to simply spoof my credentials and becoming able to read my records from the DoD, NSA, FBI or IRS (All organizations I contracted for or given a large sum of my paycheck to). These things are far more important than the convenience of being freed from memorizing a separate set of credentials.
SSO systems are only good for trivial things, such as allowing me to use the same creds to log into my Hotmail account and my TechNet and MSDN subscriptions. None of which contains anything highly sensitive, and most of the info is false.
This is just foolish, rather than the Government tracking your every move (As is the case in of the UK) the US is moving to where now big business can do so. Despite what they say, companies WILL monetize your information (Particularly advertising companies such as Google)
Call me paranoid, but this is how it happens, they take away little pieces of your privacy at a time and you will one day wake up to find that your every move is being tracked in order to sell you something, or even worse, to keep you in line when they grow bored of just controlling markets and move to controlling entire peoples and the destiny of the human race, to become gods.
My personal feeling is that a person willing to give freedom for security deserves neither, but a person willing to give up their personal identity for convenience deserves nothing.