Just in case anyone has doubts about the alternatives in this thread. . . . I bought the MCE Optibay for a 2007 MBP that was just out of warrantee. Got the empty one so I could add my own HDD. I thought I was paying for quality and customer service and I wasn't.
The website says it comes with a user guide. The user guide DOES NOT include instructions for installation for my model (it does for unibody models). It's not that hard to figure out (I'm not that handy and I did it) but there you go.
More disturbing is that the optibay model for the 2007 MBP does not have any kind of front barrier. Which means that someone sliding a CD into the slot for where your CD drive used to be will hit your hard drive.
I was a bit floored that they didn't even include a simple cardboard barrier. It looks like there should be one. Also, two of the screwholes in the bottom were a little off center.
I called them to ask about these two things. The tech said "they are working on a manual" for the optibay for the 2007 MBP. Since they have manuals for all the others, all someone needs to do is snap some pictures and edit a little text. He also assured me that the optibay "had been tested and kept CDs out". This is also patently false as anyone who doesn't know there's no CD drive in there could jam something up against the hard drive. In classic tech support fashion, the tech treated me like an idiot for being concerned about this.
My solution? Electrical tape over the opening so it will block a CD or DVD before it hits the drive.
Does it work? Yes, 100% and it's great to have two drives in my laptop. The external enclosure is also just fine and even has a front now (earlier purchasers complained about the lack of a front).
But I do have a bad taste in my mouth. I thought I was paying $100 for kludge-free quality and a little customer support (like the instructions promised on their website or a non-rude phone tech). Apparently not.
So I would definitely recommend others investigate the cheaper solutions, especially for first-generation Macbook Pros, before giving this company your money.