Windows Experience Index

The Windows Experience is still there--even in build 9860.  However, the GUI was retired with Windows 8.  If you want to run the experience, which is really called the "Windows System Assessment Tool," you must run it from the command line.

Open an administrative command prompt and type winsat formal -v -xml c:\winstatresults.xml.  This will run the full formal test in verbose mode and provide an xml output of the results.  It is in the report, you will see the scores you seek.  As others have said, it is important to keep in mind that the numbers may not--probably won't--really align with the numbers from previous operating systems.

Another thing to keep in mind is that all of the preview versions and builds are "checked" builds with debugging code built in.  As such, preview versions of Windows will never run as fast as "free" builds that are fully optimized and lacks all of the debugging code.  This is the reason why Microsoft insists that people don't run and publish performance testing results as the test is not an accurate or fair measure.

If you want to run just a subset of the tests, type winsat /? see all of the arguments and options.

Navigate to C:\Windows\Performance\WinSAT\DataStore to see all of the assessment XML files.