The single meter was the de facto system in both ME1 and ME2. It was simply not practical to have one half Paragon, one half Renegade, because it didn't help you with anything. The game was designed to make you pick between paragon and renegade, which is a design flaw, in my opinion, because it takes a lot of choice out of the game. In fact, the less choices you are given (i.e. just go renegade in spite of personal preference) the more choice you actually had later, because you could persuade people, but you could also shoot them in the face. If you did whatever you wanted then all you could do really is shoot people in the face and take the long way round. So this is Bioware just saying, yeah, this is how it is, deal with it. I don't expect Shepard to get a neutrality bonus, which would actually be harder to get because it would be difficult to actually balance one system of morality versus the other.
The rest of the system looks the same as ME2, except blue, as other people have pointed out. Hopefully, there will be more customization.
I wonder they will justify Shepard losing all his abilities this time 'round.