Review: MaxConnect USB External Enclosure for Unibody MBP Optical Drive
tl;dr: A good way to get some use out of a displaced internal SuperDrive. Case design has its flaws, but it works pretty well.
If you want to make your MacBook Pro a true mobile workhorse, there are few things you can do that are better than adding in a second hard drive (for capacity or RAID), and/or swapping out the main hard drive for an SSD and loading your OS onto that (it's ridiculously fast!).