DIY Gamer has a nice profile on Global Agenda. It's on sale for $7.50. Thanks to the "Friends with Benefits" promotion, I joined the game for $15 myself, after the generous free (up to level 12) trial.
I write the following as a genuine fan, and not a journalist or promoter.
Hi-rez studios is a small MMO that's has no subscriptions. They offer some standard freemium offers such as booster packs and the like, and the initial software purchase is normally $30. It's a small little MMO with a great community of players. Rarely are there players with an anti-social attitude. Indeed, the game encourages the formation of guild-like "Agencies" that can be made up by friends made early on in the game.
Global Agenda is set in that typical post-apocalyptic world of which other Unreal sci-fi games are so fond. It draws from so much science fiction to create a nicely fleshed out sandbox of an MMO - there's a war between robots and disparate human mercenary gangs known as "agencies". That's it. Everything beyond that is player driven.
Levels 1-19 is a tutorial of sorts. It introduces the mechanics of the game, the basic conflict, and the desert that surrounds Dome City - many players' base of operations.
After this, there are selections of Player vs. Environment missions, Player vs. Player, raids, and the like. However, where the game shines is in Agency vs. Agency (aka AvA). The meta-game is a risk-like game in which agencies compete for territory. More territory means more power, of course, and hen struggle goes on ad infinitum.
Despite this competition, the community is largely friendly and open to teaching newcomers. Largely this is due to their desire to recruit and train good future agents.
It's an excellent design, and fun to play. However, there are some slow periods, as with most multiplayer games.
A friend of mine and fellow Zircon agent wrote his own review of the game.