TotalBiscuit's WTF Is... suggested that the vast majority of the game (90% in his estimation) is just roaming around the island blowing up 'chaos objects' and liberating towns/cities/bases, and that you have no choice but to do that as the story missions are gated behind doing so. Apparently it gets pretty repetitive. The side missions also look pretty dull, unless you like driving things through giant rings, but you have to do those too as upgrades are gated behind them.
Really it seems to mainly be a massive sandbox where you can blow things up to your heart's content, without much beyond that. I guess that's fine, given the low price (picked it up for just over £16 personally). Performance on a GTX 780 seems reasonable, but v-sync is a no-go since it has no triple buffering, so crashes down to 30fps when the framerate drops. Forcing it via the control panel seems to have no effect.