The shooter part of the experience is a bit meh to be honest, but that shouldn't hold anyone back from playing it because the storyline is fantastic. =)
Although to be fair (*MINOR SPOILER INCOMING*), the inevitability of the plotline kinda cheesed me off particularly when you start slipping between worlds as an unwitting passenger more than a participant
Kinda like those games where your character would either ignore something blatantly obvious for the sake of the big *surprise* moment (ie. the player sees "it" coming a mile away whereas the character remains frustratingly ignorant) or where you're offered a choice that almost no logical person would take (the bad ending of Far Cry 3 comes to mind where you are expected to slaughter the people you just sacrificed your humanity and sanity to save). I like to feel involved in the narrative, like your choices actually matter even if the outcome is inevitable, rather than superfluous to it.
I wouldn't ever bother with DLC though, the game and story are completed at the moment and going back to fill in a little blank here and there just makes no sense to me.
Asmodai aka Saviourself aka Stabbitha aka Azshadoria... or Azsh... Azshaz?