So, I just finished the campaign. Overall I feel that it's better than Battlefield 3's, but it's still nothing to write home about. Here's a short list of comments off the top of my head:
+Slightly more open level design allowed for different approaches to encounters
+Being able to choose whatever weapons you wanted also added to this variety
+Gameplay tries to teach you the basics of multiplayer more than BF3 did
+Being able to freely enter and exit vehicles in certain areas
+No real QTEs
-There are still a lot of scripted unskippable sequences
-Having to wait for your teammates or stand in very specific areas to trigger events
-Story was, just like in 99% of military shooters, unimpressive
-NPCs keep specifically complimenting me and only me for my actions or even for our entire squad's actions
-NPCs calling out that the area is clear the second I kill the last guy in an area every time
-Still no flying section
-Levels still very linear compared to multiplayer
-Smaller scale battles than in BF3
-Very short, finished it within 5 hours
In the end it's slightly better than I expected, but that's mostly because I went in with basically no expectations anyway. I feel like if DICE wants to create a campaign that will grab the players as much as mutliplayer does they need to turn the game into a sandbox game. Think something like Halo or Crysis 1 (first 2/3 of the game), but with Battlefield's weapons, vehicles and equipment. These aren't open world games, but still offer wide open maps which allow you to approach encounters and a lot of different ways. Why not have huge battles with tanks, helicopters, infantry and all the good stuff and allow the player to choose whatever weaponry they want? That's the kind of stuff that people play for multiplayer for. BF4's campaign showed this kind of approach in a handful of moments where you overlook an area with the option to approach it in multiple ways, but I think taking that a step further would improve the game a lot.
Sigh... maybe in Battlefield 5.