I went and picked it up last night and put about an hour into it. Had to update to the latest beta nvidia drivers to get it to run though.
Without the time aspect, it is a bit more of an average shooter; a little too linear with very good graphics (and needing the horses to push it), weapons are somewhat standard although graphically unique and all having a secondary fire method is a bonus. The storyline is still somewhat disjointed as you start by watching as the lab blows in the beginning, and then get warped to a city battlefield with some very cool looking large robots walking around.
Throw in the time though (except for reverse-time to a degree as that seems mostly story/script driven in use) and to me it does push the overall "grade" of the game up several notches. Walking through the ruins to hear a door busted in and a bunch of baddies suddenly light up your radar scope; hitting time slow and then running to the entry while mowing down the first couple guys, then entering the room they are coming from and taking down most of the backup, and then watching 8 of the 10 drop once time goes normally speed and the remaining guys start shouting things like "what happened, he's over there": a pretty cool event. It becomes even more fun once you've got the automatic double barreled shotgun and do this, get some nice big blood plumes that hang in the air after you shoot until time catches up and it all drops to the ground.
Haven't tried multiplayer yet and don't know if the time aspect has any effect there, although it seems that it could be odd with different players using time at different times.