Doesn't matter.
Joe ran on "democrat, except on Iraq / National Security" and won easily, even after loosing the primary, so I'm sure he feels comfortable in that position.
If you were somehow single-issue enough, you'd be more comfortable with Joe than about a dozen republicans I could name just of the top of my head.
I don't understand how you can think that he will change his stripes. Maybe people think Joe will spite the rats? Joe is going to do what is best for Joe.