I've not really studied them, as anything that only relies on net/cloud based* services isn't going to be very useful for most of the locations I visit here in China. (Wifi is still far from ubiquitous here, even in the major cities). I think that, eventually, most data will be stored 'on the cloud**' and there will be a wifi-like connection covering the entire planet, but that's some distance away. Until that's the case I think I'll stick with my PC/pad/phone.
*Also China doesn't like Google very much, so that would be a bit unreliable.
**Which you must remember is still stored on hard disks, just one in some massive data center somewhere.