Yes. I've had major midgame performance issues since launch. Graphics get choppy and there is quite a bit of lag after I reveal more than a small amount of the map. Reducing the graphics options helps a little bit, but doesn't resolve it. This has very slightly improved since the patches from launch to make it playable midgame, but it still makes it quite a drag.
Also get a fair number of crashes as you are.
My computer runs modern games fine (including SoaSE: Rebellion, Witcher 2, Crysis 2), but always has issues with this game which is less graphically intensive.
Intel Core 2 Quad CPU
Q660 @ 2.40 GHz, 3.37 GB or RAM
Video card: NVIDIA, GeForce GTX 560 Ti, latest drivers installed
Again, this system is not the newest in the world but it handles most modern games just fine. Would be interested in hearing if others are having this issue as well and any fixes.