I noticed that I have a significantly lower FPS in multiplayer than in single. I can have 50 AI soldiers in one scene just fine, but 30 or 40 in MP slows me down to ~20fps. The performance hit varies from server to server but it is always there in some form.
My PC specs are as follows:
Asrock Z77 Extreme4 Motherboard
Intel i5 3570 (non-OC)
Galaxy GTX670 GC
8GB G.Skill Sniper RAM @ 1866mHz
Thank you for your time.
P.S. I also noticed a bit of texture Z-Clashing inside destroyed buildings, though this is a fairly minor issue.