I'm optimistic about this new system. I've recently been using them more often to get things such as animals and odd parts that I don't think it is worth buying the sets for.
Ever since I knew Bricks and Pieces was different from Pick a Brick, I've been wondering why these weren't the same thing to begin with. It sounds like enough people have been finding it for specific parts and the usage has increased enough that they can justify the investment into the system design.
Perhaps in the future, this will combine with Bricklink for how they distribute parts. They could also reproduce parts that have been out of production and are in demand. That would really excite me (Monorail anyone? Heh heh).