I purchased the Freecom XS 1TB external hard drive just before university. From browsing and searching at the time... I found that this hard drive was the cheapest at the time, and also had the best size with regards to portability. Freecom have a large range of data storage related products ranging from 1.8" hard drives (the size of an iPod Classic), 2.5" hard drives (ones that are used in laptops) and 3.5" hard drives (ones that are used in desktop computers). As the Freecom XS is a 3.5" hard drive, it does come with an AC plug in order to power the unit. The drive also comes with software that can be used to improve the overall transfer speeds of the drive and also encrypt the hard drive itself.
As I have been using this as a backup solution to my mac / windows computer, I have found it very easy to use and modify when needs be. Out of the box it is compatible with both Mac and PC as it is formatted to FAT32 (which is the primary storage type used in USB flash memory sticks). The limitation with this is that FAT32 has a file limit of 4GB... which means anything above that size cannot be stored onto the hard drive. After researching there are a few options I would recommend doing.
If your Mac is OS X 10.6 or later ... or your PC is Windows 7... I would recommend that you re-format the hard drive to exFAT. This has no limitations to what file size you store onto the hard drive and both Mac and Windows can read and write to the hard drive (based on the operating systems I stated). A second option would be to format the hard drive specifically ... so if you are using Windows only as a whole, NTFS would be most beneficial. If you are using Mac OS only as a whole... "Mac OS extended (journaled)" would be most ideal. By doing this the hard drive will be optimized so that it would be best configured for the particular operating system.
The third option would be to partition the hard drive depending on how much you will use for your Mac / Windows computers. For your Mac partition I would recommend you use "Mac OS extended (journaled)" and for your Windows Partition I would recommend you use NTFS. By doing this the hard drive partitions will be working at the best optimum level accustomed to the operating system and you will have a best of both worlds in a sense.
After a year of usage i found this hard drive to be a good solution to expanding my storage space and easy to use when needs be. Initial installation of the software was easy to do, but when using the software I felt the transfer speed ability was somewhat lacking. The hard drive only had a slightly faster transfer speed rate.. maybe 1 to 2 mb/s faster.
I feel the original transfer speed rate is very good considering it is external storage. Flash memory USB sticks are somewhat slower than physical hard drives... yet SSD drives are significantly faster. If you want a faster solution... go for a Solid State Drive, but please consider the factors of a significant cost increase (a little over £1 per GB) and the fact that at this moment in time; you cannot have a very large storage size with an SSD.
At the time of purchasing I purchased this hard drive for £55. As this was purchased in August 2010, you can see that hard drive storage capacity prices have fallen considerably over the past year... due to being able to purchase 2TB worth of storage for the price i paid a year ago.
I would recommend this hard drive to anyone wanting an ideal external storage solution at a good price. It does exactly what you want it to do and performs well when wanting to backup or generally store files on it.