◾Mantle performance for the AMD Radeon™ HD 7000/HD 8000 Series GPUs and AMD Radeon™ R9 280X and R9 270X GPUs will be optimized for BattleField 4™ in future AMD Catalyst™ releases. These products will see limited gains in BattleField 4™ and AMD is currently investigating optimizations for them.
◾Multi-GPU support under DirectX® and Mantle will be added to StarSwarm in a future application patch
◾Intermittent stuttering or stability issues may occur when utilizing Mantle with AMD CrossFire™ technology in BattleField 4™ - AMD recommends using the DirectX code path when playing Battlefield 4 with multiple GPUs. A future AMD Catalyst release will resolve these issues
◾Notebooks based on AMD Enduro or PowerXpress™ technologies are currently not supported by the Mantle codepath in Battlefield 4™
◾AMD Eyefinity configurations utilizing portrait display orientations are currently not supported by the Mantle codepath in Battlefield 4™
◾AMD Eyefinity technology is not currently supported in the Star Swarm​ application
◾AMD testing for the AMD Catalyst™ 14.1 Beta Mantle driver has been concentrated on the following products: AMD Radeon™ R9 290X, R9 290, R9 280, R9 270, R7 260X, R7 260, HD 7000 Series, HD 8000 Series, A10-7850K and A10-7700K. Future AMD Catalyst™ releases will include full test coverage for all AMD products supported by Mantle.
◾Graphics hardware in the AMD A10-7850K and A10-7700K may override the presence of a discrete GPU under the Mantle code path in Battlefield 4™
◾Frame Pacing for Dual Graphics and non-XDMA configurations above 2560x1600 do not currently work with Battlefield 3 and Battlefield 4. An upcoming release will enable support
◾DX9 Dual graphics is not supported in AMD Catalyst 14.1 Beta. An upcoming release will enable support

This is what removed my stutter with Mantle:

BEFORE, I used to have the render ahead limit at 0. With Mantle enabled, I got some serious stutter after like 20 seconds, no matter what happened.

I set it back to 3 and there is NO stutter at all.

SO I recommend this to all the people that have stutter problems with Mantle.
Won't guarantee that it also works for you, but at least give it a try if you haven't already!

Edit: This is the very first time I can play Shanghai at a constant 60 fps, no matter where I am or what's happening.
2500k
R9 270x