Many other drives work fine. I installed a 22x (I think it was a samsung?) a few years ago and it works great. Couldn't tell you exactly which ones will or won't work, but I'm sure if you did a search on Google for Mac Pro upgrade DVD or superdrive, you'd be able to find a list of known good ones.
Installing the is also easy. You just pull the old one out ,unclip the power, plug in a new one and push it back into the slot.