EDIT Dec 2015- this is an older model now the amazon listing should be your first port of call for checking this new model out but really expect much of the same. This works out of the box in extending your XBOX ONE internal memory ! Awesome news indeed.

Older model review follows...[EDIT End]
I just took possession of my western digital 'MY PASSPORT' USB 3 portable hard drive. I got it for my Mac Book Air (MBA). I am very happy with the weight the size and its damn sexy. I went for blue. Its a 1TB model and it was pretty much plug and play the MBA spotted it needed formatting straight away and also defualt TIME MACHINE for me. Its wonderful being a part of the mac eco system. You must read more of this if you are in the market take advantage of my research as always and desire to get the best value and stye in products.

This is not the thunderbolt port that is available on my MBA but I reasoned that I wouldn't use the speed USB is a lot faster 3 times as much as USB2 I read. And USB is simply more available for other devices.
I just plugged it straight into my mac USB 3 port and voila it recognised it and prompted me to format it. This drive is pre configured for windows but MAC daddy not worry just formatted on the fly and then auto asked me to use Time Machine with this - yes indeed I did and followed the screen prompts see some of the photos.

It comes with a 2 year limited warranty and a decent enough sized USB3 cable.