Good points:
-The weapons "feeling" are good, I liked the design and sound of all of them and there wasn't a single weapon where I found odd to use.

-I kinda liked their perk system, it's useful to balance your team if you have enough map experience and if you're going to play with a know team or with random people. Can't say about the future monetization of this part (pay to win maybe).

-I liked the abundance of random items through the map, you can decide if it's worth to change your current weapon or if it's worth to take the tool box to open some doors instead of a ammo box, a defibrillator instead of a med kit, etc.

-The button to inform you found something to others it's a thing that I miss in l4d games, so it's a very good addition

Bad points:
-The campaign is huge, I know this can sound nice but after some time it really get tiring of it. A normal l4d campaign is usually 35-50 minutes with an average team, but in B4B it take almost two hours to complete a campaign. It also has the 3 chances thing, where I failed in the final act because neither me or my team knew what to do to shot the cannon (we had to remove the "used ammo" after firing up) and I discovered it just after we lost 2 continues. In the result, 2 hours wasted because the objective wasn't clear enough. Same where there's a part when we need to rush the mines and I only knew that because a guy from my team knew it before.

-The balance of the campaign difficult parts are also bad, it's either too easy passing through the same bald common zombies (which become a little boring after some hours) and almost no special infected, or too hard when you're in a objective part of the map and the game start to spawn a endless horde of special infected (especially those big arm ones) there you'll pretty much waste all your ammo on it (and hope the rest of your team know what you have to do to progress).

-The game can be a little confusing, Like you have to pay attention and stop to read things in order to understand what's the item does or what we'll have to do. I really missed something like the director [External Link] to help me making my decisions and is too much information for someone not used to this kind of game system. I'm glad in this case was localized to my language, or I would have to explain to my team wtf we need to do (I had anyway, but it was easier than a game entirely in english)

-The experience with the characters were a little... generic. The same bold zombies everywhere, acting the same way, and the fact that you don't really need to take care of each other until the infinite hordes part make me feel like no difference in playing with bots or random players. Also the voice acting is not very expressive, I almost didn't pay attention to what the characters were saying, the subs were just the same generic white text and paying attention to it would mean my team rushing without me.

Conclusion:
This game doesn't feel like a "left 4 dead 3" for me, it's more like a mix of Warhammer Vermintide + Zombie Army Trilogy, and while it's fun in the beginning it felt like one of those games where you can get bored very fast and don't know exactly why. Playing it showed me how ahead of his time Left 4 Dead is and how much the lack of Valve support impact in Turtle Rock Studio games. Back for Blood it seems like a game with potential but I can't recommend it in the current price.