Yes, but its kind of wonky and being broken/abused by the early adopters. Mm has mentioned a fix is forthcoming -- it's one of their top priorities. I think long-term the wheat will separate from the chaffe via word-of-mouth on the Internet forums and review sites, where users will just be directed to look to favorite levels by specific authors.

I would not rule out Mm releasing "map packs" themselves, or coordinating with the LBP community to make sure the cream rises to the top among the user generated content.

^ People "Heart" levels they like and the number of hearts are shown with the level description.

There is no starred ranking yet but whenever you play an online level you are asked to rate it. This means that such a ranking will be in the next update to the game....