To me Siege of Shanghai is not a good map although it does offer up a style of play quite different to 3. I'm currently pitching in with other BF3 admins for a BF4 server and we know for sure this isn't going to be on the rotation as we settle on one map. Overall there are a good few improvements made, the overall feel is decidedly more arcady (good or bad depending on who you are), there are balancing issues that one would hope would be addressed and there have been some technical and networking problems on the PC side that I can't imagine will all be fixed with the release so close. It does look fantastic despite plenty of unfinished textures, shame about the current-gen console versions.
 one welcome change is the cooldown on vehicle ammunition, namely the chopper gunner that can't spend the whole round firing non-stop, taking on targets is now a more considered affair.