The beta program of this services was restricted to players near single data center in San Jose, is now expended to US and will be available to other countries but requires to build Local Data center.
Resolution is restricted to 720p, which is quit good as data has to be sent to local data center and in return is to be received. According to Nvidia user will be needing 10mb downloading speed for better experience. Game experience is same as PC version and controls are same.
Initially the 20-odd games were included to play for free, and Nvidia says new games will be added on a weekly basis.
The Nvidia Grid cloud gaming service serves up around 20 PC-based games for free, but only to a handful of devices. Grid does seem like it could easily scale to other Android devices or even to Windows PCs.