I have one of these, it works perfectly. I was out of HD space on my 128GB MBAir and I kept getting that "start up disk almost full" warning so I bought a 256GB TarDisk Pear.
Was much cheaper than a new computer, plus I get to keep my current computer which I love

. You do have to restart a few times during installation, but I already had a Time Machine back up made so it took like less than 10 minutes to install. Would definitely recommend.
Lanre I think what you're talking about is the cloud backup option. They offer a free cloud backup of your whole HD during installation. I didn't go for it because I already have Time Machine, but It's an option for people who don't I guess.