Sufficiently Advanced is semi-hard sci-fi done very well. I call it "semi-hard" because the degree of "speculative" in the science might make some people think it a little less "hard" than it should be. However, the setting is well done, with enough detail and scope to give you plenty to work with and enough room left behind to give you plenty of room. The setting is a transitory one, at several points telling you that the current state of the universe isn't going to remain forever, and isn't intended to. However, there is no actual "metaplot", in that there's no one way the setting is supposed to go.
The system is made up of a neat balance of immersionist and narrativist gaming. Despite not liking most narrativist games (more of a simulationist/immersionist myself), the narrativist element is extremely well done, with characters bringing their own tropes with them where they go. The system is very flexible, and allows you to play as functional characters anything from a poor old unaugmented human to the most advanced posthuman conceivable within the confines of modern science.
The game also gets considerable support online at http://suffadv.wikidot.com/. You'll find some of my contributions, as well as those of many others, there, including ways of bending the system and setting to better reflect your way of gaming or your envisioned future. Both system and setting are very flexible within limits.
To me, the only downside of the game is the general focus on playing Patent Officers. Intellectual property is the only property of any significant value in the setting (since you can replicate any substance you want), and the Patent Office is extremely important for policing the international economy, making it rather like a World International Property Organization with police enforcement powers. Awesome as this is, there are times I want something else. However, the game is not so dependant on this concept that you cannot break from it. The game's open to other concepts, it just isn't as supportive of them.
[5 of 5 Stars!]