MacBook Pro HDD Swapping?

So, there's this company called MCE. They offer a bracket that allows you to swap out your optical drive for a second HDD.

MCE OptiBay Hard Drive for Unibody MacBook Pro 13", 15" and 17" and Unibody MacBook 13": MCE Technologies Online Store

They offer a service that installs the bracket and the HDD. They also allow you to install with a provided guide. My question is, does this void my warranty?

It's definitely shaky ground. Apple considers the hard drive and ram as being user-serviceable on these models, but they don't mention the optical drive. I can definitely see them refusing a warranty repair if a modification like this were undertaken.