Yes, it's annoying when some creep goes through and decides to have fun trashing peoples' ratings. But this is only the annoying exception, not the rule. I say keep the ratings system, it's nice to see what people think of a certain skin, even if it's only the opinions of 2.5 people. As for when people have trashed my ratings, in the past I've had some friends go through and artificially restore the rating back to where it was. One thing I would like to see on the ratings, is how many people have rated the skin.
Likewise, keep the download numbers, it's nice to see that enough people like my stuff to get 20,000 downloads in a month. Even if feedback systems aren't perfect, and they never will be, they're still useful and often brighten someone's day.
I also say keep the top authors section as it is for two reasons. One, it's nice to go into the detailed secion of the top authors and see where you personally rank. Second, it's a good way for newbies to see some really great skins without having to wade through everything. Yes, it artificially inflates their downloads, but I don't really consider that to be a problem.
Same with the top downloads section, yeah sure, some don't really "deserve" to be there, but most do. When I'm just doing a quick pass through the site I'll often visit the top downloads section to see the best stuff of the week. One complaint I do have about the (short list) top downloads section is when more than one element of a suite is on there at a time.