So I received my MCE Optibay yesterday. A few observations:
The MCE optibay is made to a much higher standard than the bay I got off Amazon. The metal feels more solid, the finish is nicer, all the holes are there to screw it down properly (the Amazon one had none). If fits properly in the bay.
They also shipped a bag with extra screws, a CD with installation instructions, a tool with two sizes Philips head at either end, and a USB bay for the optical drive coming out of the MBP.
My only gripe is that the two holes at the back, where the bracket in the MBP attaches to, didn't have screw thread. The only thing I had to (force) make it with is the screws, and in the process I damaged the head of one.
Mone well spent, IMHO. It fits propery, it's properly attached, my laptop doesn't have that annoying micro-rattle sound anymore.