I played through nearly all of Darksiders on OnLive and half of Batman: Arkham City through their microconsole, and as long as no-one in the house decided to peer up with 300 other users to download the latest episode of Game of Thrones or watch porn, its a very very comparable experience in a small, cheap package to what you'd have to spend hundreds to get otherwise. I'm in the UK, and the ISP was O2. I tried it again with Virgin and Sky and it wasn't so good... but I was convinced completely. Being able to play any game, try ANY game, for 30 minutes - before I buy... that's just brilliant. No downloads, no waiting for discs in the mail, it just works instantly. The network infrastructure might not be there for everybody just yet, but this is going to be how its done when it is imo. Like others have already suggested, we could be buying TVs that just do this shit as standard... no more box under the TV.
It's going to help drive innovation from Nintendo, Microsoft and Sony - because they'll all want to keep us buying something, they'll want to offer some new fun proposition that can only be had with them... all in all, the future's pretty bright.