What's New and Different:
We can, however, still talk about some of the changes. The first question people are going to have is, "Can I jump from BF3 straight into BF4?" The answer is absolutely yes. It's not just that the game is designed to be approachable, but that it plays almost exactly like its predecessor.
That said, there's a lot of clean-up around the edges that improves the experience. Many of the vehicle and weapon models are the same, but the particle effects, colors, and explosions of the new maps are brighter and clearer. The audio engine appears to have been significantly boosted; sounds are sharper and gunfire is more satisfying. The weapon loadout screen is easier to navigate, and the tactical map you see in between respawns shows you what's going on at the various spawn points or in available vehicles. It's a vast improvement over BF3, and gives you a clearer idea of whether the vehicle / person you're about to spawn on will be dead two seconds after you hit "Deploy."
Health (both player and vehicle) regenerates very quickly in the beta, substantially reducing the need for medkits. The beta's single map, Siege of Shanghai, features a gorgeous demonstration of what EA/DICE call "Levolution" -- the idea that the game map can change dramatically depending on player actions. If you're familiar with the Battlefield series' destructible terrain, this is a further extension of the concept. No, buildings can't be completely leveled ala Battlefield: Bad Company 2, but the idea behind Levolution is that players can cause enormous changes within specified areas of the map, thereby shifting the balance of power on underlying terrain.
EA's official Levolution demo and gameplay demonstration.
EA/DICE's Levolution system is also responsible for the fact that these new maps are more interactive than their counterparts. Players can go up and down in elevators, open and close choke points, and manipulate more environmental objects than was previously possible in BF3.