A brilliant concept and a great way to view some alternative plots within the storylines that every Marvel fan knows, but horribly inconsistent. Some can lack any real power, Captain Carter not being too captivating although an interesting plot, T'Challa as Star Lord being a little too perfect, but others, like the murder of the Avengers are engrossing. It's just so disappointing that an episode such as Dr Strange losing his heart, which is poetic, powerful and beautiful, can be followed by the most disappointing Zombies episode imaginable. Zombies, was a particular waste.
The animation is okay, distinct enough to be recognisable as it's own thing but not so easy on the eye. Keeping the vast majority of actors to voice their animated counterparts is a win, but sometimes the writing just isn't good enough. I'm thinking of the Zombie episode again, what a swing and a miss.
EDIT: Nothing is as bad as the Thor as an only child episode though. Painfully unfunny, shockingly bad.