GameFly streaming is a bit like Netflix
For a monthly subscription fee of $7, you can have access to one of a group of game packs with 7 games each, or for $10 a month, the Gamer Pack, which includes Darksiders and Batman: Arkham Asylum.
Game data is saved on the cloud service, and is not deleted even if you unsubscribe. There is a local mutliplayer option, but apparently no online multiplayer. Graphics options cannot be altered for each game, and only one game may be streamed at a time.
The service currently suffers from a lack of available titles, as well as intermittent lag
While there are 51 current available titles on the streaming service, what games are available depends on the subscription you have. 51 titles is relatively sparse pickings and narrowing that to 7 (or 16 if you have the Gamer Pack) based on subscription does not help the cause.
According to Ars Technica, when they tested BlazBlue, Ridge Racer Unbounded, and Pac-Man: Champion Edition DX, all three of the games experienced occasional, intermittent lag. They also noted that the graphics did not reach the promised 720p resolution:
Ars Technica noted lag and lower resolutions in their article on the new streaming service.
GameFly’s own words on the purported quality of their streaming are something else to consider:
GameFly would claim you can play games uninterrupted, but Ars Technica’s tests, on the best consumer-grade Internet connections available to those in the United States, would seem to prove otherwise.