I'm not disappointed that IP doesn't play well, because EA never stated it would play well or even great. It's been said quite a few times that bigger towns like IP will have lag and stuttering issues. There's tips and tricks to help, but they aren't going to play well on every system - because every system is different in some way.
If possible, you might try adding an SSD to play the game and use your hard drive to save. However, I can't promise that will definitely help the lag and stutter of IP.