I'm about to buy a pair of 750 GB drives since I've used the capacity on my 500s. I'll move the stock 250 to an external enclosure, and replace it with the 750 and use the other 750 for back up. (I assume I should just install the OS on the 750 and then use the transfer utility from the 250.) Going on the OWC website, there's a plethera of 750 options -- and I've usually purchased Seagate or WD. They're all within $30 of each other, but the Hitachi has a 32 mb buffer, whereas the other 2 are 16 mb. Of couse, the Hitachi is cheaper -- and since I believe there's no such thing as a free lunch, does the 16 versus 32 matter, and am I just missing other intangibles out there that Seagate and WD have. All are 7200 rpm.