It's a 7 out of 10 at best. It's a fireworks show and as such it works.
I'll keep it spoilerfree
Every character has joke on the tip of their tongue, at all times and all the characters sound the same. They use the same words, the same speech patterns and are too shallow. It might have the corniest moment of all superhero movies, and that saying alot.
Thank god Joss Whedon isn't doing another.
All the effects are great, except for one. It's like 0.5 secs so many might not notice but it's shocking it got shipped like this, this will most def. be fixed for the BluRay.