I've been experiencing bad lag issues since I8. Frame rates are erratic, ranging from 30 to 1.5. Solo missions run ok, with frame rates from 8 to 15 on average. Team play gets pretty choppy. I've dropped my graphics settings down to medium and low on most settings. I'm running an nVidia geForce 6200 256MB graphics card on AMD Athlon XP 2700+ processor with 1.0 GB of RAM. I'd noticed some lag in large teams before I8, but things have gotten ridiculous since.
I hope this helps.