5.3
Basically it tallys your system against a base score of 1.0 and then gives a rating. The overall score is simply the lowest score you achieved out of them all. Soon alot of software will not have system requirements listed on the box in detail anymore. It will simply say "you need a windows experience rating of 3.0 to use this software but we recommend 4.5 for the best experience." or something along those lines.
It's easier for people who have no iea how much memory they have, what type of video card they have, how fast their CPU is. Most people buying Dell etc really wouldn't know all the little details.