Advantages are you will not need a console of your own, can use multiple devices to play the same game, and you can play anywhere. It's essentially like Steam without the required download.
They also asked for a server programmer for a "Triple A MMO game"
Wonder what that is?
As for gaming on the cloud, I can see it being popular in countries outside of the US because they have the internet infrastructures to support it (while US is pretty slow for a developed country) you simply can't play cloud computing if you have a terrible connection.
Cloud based gaming will not be a hit with the hardcore due to the latency involved. Back in the 90's a difference of 10 ms was crucial to who got the kill shot, looking at todays gaming it still holds true and nothing can predict that Onlive is based on prediction of movement, not on when player x decides to shoot. Until latency is sub ms it will never appeal to the hardcore.