Absolutely! When I first started learning how bukkit worked and looking for plugins to download back in the early days of SMP I remember thinking how nice it would be to see the "most popular" plugins to help me get a feel for what my options were. to this day I would love to be able to sort by rating when browsing to weed out the crap, and help me find the cool stuff I may never think to look for otherwise.
i'd be happy with something as simple as a "I use this" button to provide a count. Gives us more of a popularity rating. And it turns into a "I no longer use this" button for when something better comes along. problem with full rating is , some people will mark it based on how well they like the author, or the author's other plugins. And if it has one little thing wrong, they might only give it 1 bucket, even though they use it because they like everything else about it. (that kind of thing happens with facebook app rating all the time: 'when you implement X feature, i'll give you five stars, for now it's 1')
