Summary: I did quite a bit of research here on Amazon and other places before deciding on this particular model as my primary backup to my desktop iMac. I can honestly say, this little unit is amazing. Literally, I plugged it into the Mac using the enclosed firewire cable (which is short like others have said), a window opened on my Mac asking if I wanted to use the WD passport as my Time Machine backup drive. I said yes and with one click of the mouse, it took care of the rest.
Summary: I've had this drive for a little over a year now and I have had no problems with. It works great with Time machine. Backups and transfers are fast thanks to FireWire. The metal casing feels very solid and has protected the drive from any damage.
Summary: I've ordered a number of external hard drives on Amazon; so far, the WD My Passport Studio 500 GB is the keeper. It's portable, holds the same amount of data as my PowerBook's hard drive, and couldn't be easier to deal with--it works quite literally out of the box. Do NOT bother formatting it with the included software--your Mac knows what do do with it.
Summary: Writing this review after more than two years of owning this drive. Have had absolutely no problems with it. I have a couple of Mac partitions and a windows partition on this and its been read and written to countless times. Solid drive, but a really late review !