As the finale to such an awesome series it falls short. I can appreciate that the game still gets a lot right; there are some great moments and for a lot of my first playthrough I thought it might end up being in the same league as the rest of the series. Getting me to think that's a hell of an achievement even if it did have flaws and eventually go off the rails.
Ultimately though the flaws do add up. A real disaster of an ending - plot holes, deus ex machina, last minute villain that undermined the established villains, an a/b/c choice when we'd been promised far more and eventually an extended cut that only papers over some of the cracks - and if you play it twice you realise how little difference your choices make in the finale of a series that was meant to be all about making choices and seeing the consequences.