Hopefully the background of my decision will help you in making a decision, especially if you’re using an older Mac laptop.
Having an early 2008 Apple MacBook Pro (which I got with the faster 7200rpm 200GB drive rather than the slower 250GB one) meant my having to keep my iTunes and iPhoto files on external bus powered USB-drives for several years. Generally I use Carbon Copy Cloner for my internal drive clones to external FireWire ones, and am OK using the USB powered drives like Iomega 320 and WD 160 in the past to keep my libraries.
I did want to upgrade my internal drive to the 750GB Momentus and keep all the data in one place, but opening up the MBP, going through that hassle, and then hopefully getting an early 2012 MacBook Pro with something like a 75pGB or 1TB internal drive (whenever they come out) would mean wasted money and effort on this older laptop. So, an external bus powered drive was my practical choice for now. When I saw the 500GB bus powered 7200RPM Seagate on the shelves of the Apple Store I was tempted to buy it immediately. Then I found that this 750GB 7200RPM Seagate FreeAgent GoFlex Pro FireWire 800 USB 2.0 Ultra-Portable External Hard Drive for Mac STBB750100 version was also available in the market, and decided to go this route.
As always, ordering from Amazon was a pleasure, and even though it was fulfilled by another vendor (HPP Enterprises), even as part of a larger multi-item, multi-shipper order, everything went smoothly. The shipper was very quick in responding, understood my request to ship the drive soon as I will be traveling soon, and the drive arrived very quickly. The packaging was great from the shipper, and the Seagate packaging was OK too.
First thing you notice is how cheap, flimsy and low quality the Seagate product is in manufacture. It is a plastic case with silver sort of painted on it. It looks like some child laborer was given a spray can to paint drives, as the paint is uneven. The drive itself is light (considering how much data it lifts 🙂 ). The 2 interfaces included were nice to have, the FW800 and the USB2 to use on PCs. It came Mac formatted but that was irrelevant to me, as I partitioned it into 3 with Disk Utility.
The drive runs fine, fairly quiet, fairly fast. Not MUCH faster than the FW800 external powered ones, but quite good for bus powered. I did not notice the interface overheating as I have read some reviews mention. Pretty warm, but not burning hot. I did not test the USB one yet. The 200GB Carbon Copy Clone and even the 160GB iPhoto library moved over quite fast and without any errors or problems. Overall, satisfied with current (new) use. I cannot speak for long term reliability (e.g. the interface cable cheaply glued to the unit is said to be susceptible to breaking) but it is cheaper looking than it should be at $175 or so.
I am hoping the new MBP that comes out will have a 7200 rpm 750GB in it so I can then use this as the take-along on trips backup while larger desktop drives are stay at home backups. Hope this helps you in your decision as you consider a portable external drive for your Mac or PC. Please oblige with your acknowledgement if it is. Thanks.