"Another issue I ran into is that I got my initial invitation to Google , and built my Google network around a Gmail address (s3kur3@gmail.com). Whenever an update posts from one of my circles, or someone sends me a message, or some new person adds me to one of their Circles, Google sends me an update. The problem is that I don't use Gmail, and I don't want to use Gmail, so I never see those updates."
Of course, some of us decided to use Gmail, as the permanent address of record, precisely for that reason. When I use any other work-related email, I always have the mail automatically resent to my Gmail account. I do have some work addresses that are active, but unused simply because I don't even want to bother setting up the forwarding.
Address permanence is an issue for lots of people, though. So be careful, if you haven't already joined.