My save game says 11 hours so far, but with the minimal plot, the end game could be 15 minutes away and I wouldn't know, so I have no idea where abouts I am :/ and I really padded my game time, doing almost every side quest I could find before the main quests, optional races and such... if it matters, I'm in the second hubworld, but I'm not sure if theres a third.
It's got a good amount of variety though, something shooters are lacking these days. Enemy types are varied enough, even if some of the bandit packs are a little too similar, I haven't found a new weapon in a while, and so far, there's a decent enough selection, the car side of the game is surprisingly diverse, but once again, only just deep enough... seeing a pattern here? The gameplay is fantastic, but pretty much every element of the game brings JUST enough to compliment it, but never more then that.
Don't let that deter you though, it's honestly one of the best shooters I've ever played :3