The purpose of the slider is to tell people at a glance how much we did or did not like a game. Numerical scores will never be perfect and of course we'd all prefer that readers get context from the body of our reviews, but this at least makes it easy to tell that a 5 on this site is not "way below average" or whatever.
In the past, people would have to click through to the page that broke down scores in order to get that info, so this saves people from having to click (I don't think most people ever clicked, anyway). It also eliminates the more verbose score descriptions, which people would sometimes attributed to the writer of an individual review even though it was actually just the site's default description. Also, the new slider makes it clear that if we give a game a 3 or a 4 or whatever, that's out of 10, not out of 4 or 5.
Basically, the new system allowed me to make every change I've wanted to make for some time now, in a convenient and easy-to-read format that doesn't require a disastrous change in how we score games on the site. Ambiguity is gone and now readers can't blame us if they fail to understand what a given score means on the site. I'm happy with the new slider and I'm glad that (at least so far) others are too.
By the way, I think this review might hold the record for most posts in a feedback thread that don't actually leave any feedback on the associated review.
"Too often we enjoy the comfort of opinion without the discomfort of thought." - John F. Kennedy on reality
"What if everything you see is more than what you see--the person next to you is a warrior and the space that appears empty is a secret door to another world? What if something appears that shouldn't? You either dismiss it, or you accept that there is much more to the world than you think. Perhaps it really is a doorway, and if you choose to go inside, you'll find many unexpected things." - Shigeru Miyamoto on secret doors to another world