An issue with the auto-detection of appropriate graphics settings on a small number of hardware configurations has been identified during testing.
If you experience problems with graphics settings and performance, please adjust the settings manually in the options. This issue will be addressed with an automatic hot-fix in the next 48 hours. By connecting to Steam in 48 hours you will receive the update automatically.
Please also note that after the hot fix install, existing user defined settings will not be overridden. To enable new default optimal preferences your original preferences will need to be deleted, please refer to the following technical preference details found here