It took a while, but Sequence 13 was excellent and had me wanting more, so I played through the rest of the game.
After the build up I was disappointed to find that I wasn't able to explore Rome, but instead was constrained to a set tunnel to reach the pope. Assassinating him was easy - skirting along the rafters then diving from above - except of course it wasn't that straightforward. Lots of back and forwards, followed by a fist fight which was rigged so I couldn't best him before he'd finished his dialogue.
Then long cut scenes meeting god(s), credits, fights in the modern day, and a flimsy excuse as to why I can go back and collect anything I may have missed. I may well go back for the feathers, but I'll use a map if I do.
Great game, but with the DLC included it probably went on a tad too long. Had I skipped straight to Rome after the Spaniard had run off, I'd probably have appreciated it more. Having said that, Sequence 13 was excellent and varied, so I'm glad I got to play it ...