Here's a thread where I've asked some questions about ME and gotten some good answers:
http://www.disboards.com/showthread.php?t=911577
Since ME uses Mears, it's hard to imagine coming out even close to even if you're paying for it versus accepting the now-free ME service. But I've learned that you can only board an ME bus if you are staying at one of the "participating" resorts. If you're staying at a participating resort, it'd be a no-brainer to me: take the free ME bus.