Looks more like they are collecting email addresses...
I created a Google account specifically for Google+, then logged in to the url (above), and got the following:
Thanks for stopping by.We’re still ironing out a few kinks in Google+, so it’s not quite ready for everyone to climb aboard. But, if you want, we’ll let you know the minute the doors are open for real. Cool? Cool.
Yes, they ended the notice with "Cool? Cool."
...on the "+" side, Google is the only one to have that email address now, so I can track what happens independently of any other Google account.
Google "is out of its mind" if it thinks I am going to marry any of my established email addresses between Adsense, Analytics, YouTube, whatever else, AND new, untested social network.