I haven't had a lot of time to test it but once I decreased Dynamic Cache, frame rates are better than. 4.0. Road rendering is also a frame rate killer but 2 or 3 give me smooth frame rates for most missions. I also note that in highly wooded terrain shadow quality also has a big impact in FPS but visually I noticed very little difference between 5 and 10.
I tested a mission with visibility set to 12 km and all Ground and Terrain Detail Sliders maxed out. I had around 30 FPS. with it, where previously it probably have dropped to 12 - 15. Also smoke has much lower influence now.
Somebody notice a problem with infantry friendly fire but it didn't happen in any of the missions I played. Overall, once set up for your hardware it looks better than 4.0.