I've played through the Reassemble campaign and I really enjoyed it. I think they nailed the characters and there are some really memorable moments in the story, bigger and smaller.
The story does continue in campaign chains in the Avengers Initiative section afterwards but I haven't really delved into that yet. I think it will be missions with more dialogue before and during, but not with longer story scenes as in the main campaign. I have played some co-op with a friend though and, just like in the beta, the gameplay shines the most when you play with others.
They saved two great characters for the full game and I've had an absolute blast playing with Thor (I doubt anyone saw that coming...). Some really satisfying mechanics and a decent learning curve. For example I found it pretty hard to fly when I played Iron Man in the beta, but now that I've put in more time it feels good and I can pull off some decent maneuvers. I doubt I'll get tired of seeing enemies pinned under Mjolnir, unable to get up, or the visual of throwing the hammer at an enemy and seeing him fly off in the distance.
The game feels a bit harder than it did in the beta though. I'm not sure exactly what the difference is but it's noticeable. Perhaps it's mainly when I play solo and I've outleveled my other characters enough that they aren't helping me enough. It certainly is a lot to keep track of as well when enemies in both melee and ranged distances all try to get to you, and you stagger pretty easily when you get hit. A basic tip is to always take out turrets and ranged enemies first.
I'm on the PS4 and this far it's been clearly more polished than the beta was as well. I haven't seen any significant bugs, apart from that my friend who plays Cap became invisible during one co-op mission and there was only a shield floating around. Pretty amusing. That can of course vary depending on platform and per individual.
The pricing of the stuff in the marketplace is pretty odd though. I think they've set the prices way too high so I don't think it seems worth what you get. Fortunately I don't think there is any need to buy anything from there, especially since I personally think the best outfits I've seen are free, but with better prices it could at least be a more viable option for those that want to. Hopefully they'll reevaluate the pricing strategy, but I guess it will just depend on whether people are buying or not.
All in all I've been having a really good time this far, but the game is a lot about continuous development so we'll see how it turns out in the future. There is room to polish things and add some functionality, and there is certainly a need to put out more areas and villains if this is to be a game for the long haul.