With the proliferation of the 2.0 phenomenon, ZDNet's Phil Waineright wonders "is that a dot or a point between the two figures? Or is the punctuation silent?" If you're interested, you can see the results of a poll Wainewright did on the topic.
My suggestion? Don't say it at all. One of my first official acts as Eastwick's social media czar was to ban agency use of "2.0" unless specifically directed by clients to use it. Here is a portion of an internal Eastwick memo on the subject:
"We will not use these expressions in client communications, new business proposals etc., as they are worn out and annoying. The only exception to this policy will be use of a "2.0" term at the explicit request of a client, or when an RFP specifically calls for it. In addition to being trite, the meaning of these terms is unclear, so their use tends to interfere with effective communications."