Just started playing BF4. Got it free with graphics card. Luckily enough since it is very expensive and probably not worth it.
It's pretty much BF3 with a lot of minor improvements. Nothing gamechanging really. The "levolution" aspect adds a bit of variety but is not like "OMFG /me has a stroke!" . Weapons and vehicles have a lot more customization. The maps are nice and open with some good areas for all types of gameplay.
I can't bring myself to buy Premium yet like I did BF3... will hold out for it to get cheaper.