Google+ - is it really a Facebook/Twitter killer?

Keith Kleiner seems to thinks so.  I've not got my invite yet so cannot comment but Keith makes some interesting points about the threat Google+ poses to Facebook and Twitter.  The proof of the pudding will be in the eating; once those Twitter and Facebook buttons on Keith's articles are replaced with a Google+ button then we'll know he was right and that Google+ has done to Facebook and Twitter what they have done to Digg.