The idea is interesting, but I wonder if the average consumer will have a decent enough internet speed to have the games be both responsive and pretty. I for one am wary of lag. Then again, I've been using my Steam Link to stream from my PC to my TV and that hasn't got any noticeable delays. Can Google do the same from such a distance between server and client?
It will never fully replace physical copies for me (although I haven't bought a physical copy of a PC game in years). However, streaming a bunch of games will make it easier for me to play games that I would probably never have bought otherwise. If this turns out to be a good development, I'll probably invest in getting it.