Basing your experience on your disk data transfer rate is silly. My WEI would be 7.9 without the HDD data rate, but it's only 5.2 with it.
Indeed, the overall score is silly. I only use the subscores.
And even then, only for kicks and not as an indicator for programs to run and stuff. Maybe if more programs picked this up it would have meaning, but it's pretty arbitrary at the moment.