Just thought I'd offer my 2 cents as one who is relatively new to the site after only 6 months, is an Object Desktop subscriber but not yet a WinCustomize subscriber, and who is still learning and wanting to become an active member of the community by hopefully soon submitting my own skins, and will then be subject to the ratings.
I have not yet been able to rate anything, and even if I had been permitted, I would likely have refrained from doing so because I have seen so much controversy and emotion displayed over ratings, and frankly, I don't feel I've learned enough yet to consider my rating to be worth as much as those who have been involved in skinning longer and with so much obvious talent.
For those reasons alone, I like the proposed system outlined here, and would be more willing to rate, knowing that the weight of my rating would contribute to the whole yet not be weighted as heavily as those of individuals more experienced and knowledgeable than myself.
By the way, though 5.5 is the arithmetic mean of the numbers 1 thru 10, statistically it is highly unlikely to ever be the actual mean, median, or modal rating here at WC. I can provide some pretty interesting studies (well, interesting to geeks like me

) to prove the point if anyone really cares, but what it comes down to is a common cross-cultural reluctance to humiliate someone else.
In most cultures, it is considered rude to give severe or harsh criticism even when it is completely justified - people can usually find a reason to temper the judgement or rating. They give credit for the person's effort, intentions, or simply to encourage her/him to do better and not quit. There is also another common tendency toward leniency in any rating system, because the rater wants to be liked by the person being rated.
One last reason why the lowest rating is unlikely to be given is due to the halo effect of the moderation process. Most people will assume that since the item being rated has passed moderation, it must therefore have SOME merit, so is very unlikely to be rated as a 1, unless someone has a personal grudge, or some flaw is discovered that was missed in moderation, like it being a rip, partial rip, or just being rumored to be a rip.
At any rate, that's about a dollar's worth of my 2 cents - sorry for being long winded, and thanks for reading if you got this far.