The issue with any system is what authors would like to see over what the more abundant users like myself would be willing to do to show an addon is indeed worth the download. Some authors would like to see a way to rate beyond the standard, On an author-to-author sort of standpoint. While this gives the people doing the work to let their peers give a solid critique its still easily manipulated. Which is the main reason for taking ratings down to being with.
The closest thing in my eyes to something reasonable was what Gello posted since its still simple to use but lends 'weight' based on history. The problem with this is, as with any system is the long time users can still manipulate the numbers. Though with a weighted system it would certainly take a more intensive effort.
Being forced to post feedback to vote will just fill the comments section of a mod with simple things like 'It sucks' or 'i hate it'. There really isnt a way to force people to post actual constructive criticism. You could moderate those comments and remove the votes but that adds more (unnecessary) work for the admins.
If its any indication as to how much the bulk of the users care just look at who has replied. Im the only non-author to chime in.
There is no perfect way to do something like this. You just have to find one that bugs you the least or none at all.