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.
I've installed one of these in our Macbooks Airs at the office. Took a little bit of time because it required turning off Filevault to do the install, then turning it on after everything was complete. It expanded the storage seamlessly and has been working great for several months now.