Those of us with the 3rd party hard drive freezing issue (look for the really long threads in here or on Apple's discussion support forum) are finding that Apple says SATA II is completely unsupported in the current unibody MacBook Pros.
I'd suggest asking Apple directly, and make sure you get your answer in writing. If you have a record of them claiming SATA II support, then you have an avenue for return later when you run into problems.