I think I am hearing this complaint a lot in-game. Since 9.0 is using a lot of new code and Havok engine in the background now it is likely there will be some slower performance while they improve the code, etc. However I would just check your graphics settings and downgrade as needed to pump it back up to playable levels. All you can do I'm afraid right now from what I am hearing.
PS: Moving this to our gaming forum.