I use mine on all surfaces mentioned: hard floor, rug, and carpet. It is the only vacuum I use since I live in a small apartment, so it gets used regularly on all surfaces with its various supplied attachments.
My primary concern is that it does a very good job on the carpet (mine does). I still sweep and mop as needed on hard floor, but it's much harder to keep the carpet and rug clean if the vacuum doesn't do its job. Therefore, I would say that putting more weighting into the carpet portion of the test would be beneficial for people like me.