Faster compatible one here too (also a Samsung mechanism): OWC
That one has a power supply to plug in though, it's not bus powered. I like the bus powered for keeping things tidy I guess, and ease of storage if one doesn't use it regularly.
The speed thing is over rated IMO. I burn a lot of DVDs, 100s over the years, and even more CDs. Being able to burn that fast, and getting a successful burn are two different matters though. My 2 Pioneer internals go to 16x but I never burn past 4x or 8x for reliability. I've found that burning at max gives too many coasters on the 4 different pioneer drives I've burned through over the years. I use good name brand blanks too.
I guess if one was doing production burning all day or something it would be worth going 16x and getting a few coasters to save the 5 minutes longer it takes to burn 8x.
The Matshˇta in my iMac can never burn any disc max, I have always had to choose 4x. It doesn't have much use on it either, it's always been that way. The elderly couple I got the machine from didn't even own any blanks. I usually just take it to the old G4 with the reliable Pioneer drives.
Well iMacsoontobe, you should have enough ammo to make a decision as to what suits your needs.