So, as I understand, to use Grid you must not only have a more or less fast Wi-Fi connection (or mobile network if it allows it), but also have a device powerful enough to decode the picture being streamed from the server/your PC, right?
I've seen a couple of vids with the above-mentioned Splashtop GamePad THD - and it runs with noticeably less framerate than it does on the PC that the app was demonstated with
It's kinda strange though, because unlike Grid and Splashtop - the OnLive required to have only a fast enough internet connection which bandwith would allow to process the stream from the server, and the technology didn't require you to have a powerful hardware, meaning that you could even run things like Battlefiled 3 with maximum quality on a 5 year old PC
So why did NVidia decie to go the other way around?
To be completely honest, however, I didn't even noticed a difference between the THD version and the "Splashtop 2 version on the nexus 7 (Splashtop 2 is free so is worth a try and compatible with a wide range of devices).
May I ask you to link the video you watched to see if the different framerate could be relevant to some particular environment?