Despite appearances - specifically the vehicles, the character classes, and the open maps - this is not an attempt to make a sci-fi version of Battlefield. Nor is it, despite the name, much to do with the deathmatch tradition of Quake. It's therefore perfectly possible that fans of either of those series will be disappointed. This is, first and foremost, an Enemy Territory game.
What this means is that ETQW is a class-based first-person shooter with asymmetric, objective-based maps, quasi-realistic weapons, lashings of Quake-derived horrors, and a daunting deathmatch pace. It is a sequel not to Quake, but to Return to Castle Wolfenstein, and the free Enemy Territory expansion that Splash Damage created for it.
Most crucially, however, Enemy Territory: Quake Wars is simply brimming with possibilities. Every class has multiple weapons at their disposal from the get-go, and the vehicles, static weapons and turrets just add to the overall elaborate network of tactical variation within the game's maps, which are as detailed and expansive as they are visually impressive.
Add to this all the various vehicles and weapon load out options, and you have a game that demonstrates far more diversity of martial options than anything besides the most open-ended shooters. And it's infantry-focused too - the problems of over-used air-power are not for ETQW. You'll find yourself tackling vehicles and turrets with rocket launchers, getting down and dirty at close range with grenades and assault rifles, and finding mad uses for explosives, shields and flyer drones. It's a game that provokes invention, suicidal heroics, and momentary genius. All this, however, takes place within the (beautiful) context of ETQW's objective-based maps.