Despite having run into a couple of bugs, Assassin's Creed: Unity is far from unplayable, much less a bad game. I'm very much enjoying my time with it. Would it have benefited from a couple more months of dev time a la Watchdogs? Probably. But the biggest issue people seem to have with the game is that Ubisoft made unexpected (and probably good) changes to the gameplay but not the ones people wanted.
The microtransactions are really no big deal. They look terrible out of context, but they are just shortcuts for people who don't have the patience to amass in-game currency. Think of them as lazy cheat codes; some people will use them but they are in no way necessary.
The Initiates and companion app chests are a little more annoying but only because they pull you out of the game. Conceptually Initiates is cool because it rewards you for having played other games in the series (regardless of platform) but it's executed poorly since it uses the web browser. The companion app is largely like the fleet stuff in Black Flag except that you can only do it on an external device as there's no way to access it in game.
Overall the game is definitely worth it if you're into the franchise.