While the idea in itself is nice it also removes the players from one of the experiences that makes WoW an MMO.
While GearScore can help evaluate a players capacity for attempting a specific raid or dungeon, a rating system based on "skill" to display to others would alienate those still learning fights and how to react to certain events that would obviously be rated lower than someone who knows the fight inside and out.
Also there are certain circumstances that are uncontrollable in a raid fight.
A good example: http://www.youtube.com/watch?v=kTI4ZOZQWQw (Showing off my Raid compilation to guildees (not in circulation), I'm using it to display the part where i'm stunned in fire which happened to me the attempt prior. @ 2:00 mins in)
If I were someone else I would have rated myself low on the SkillScore based on those 2 fights alone.
Not to mention a few flaws with the theory.
GearScore tallies up gear based on the stats it provides to specific classes, and provides a default recommendation of gearscore for a particular instance, which is by all means capable of being done by inspecting a player before accepting them for a raid. Welp you have a green or a Hunter who stacks strength., sorry no raid for you, which was the case prior to gearscore anyway.
The ability to keep track of the score as was stated in a post above, would be editable, and depending on how popular the addon would be, be almost impossible to judge if the score was tampered with.
For you yourself to keep track of people and save your assessment of them would be a decent addon, maybe some automated alerts based on particular events of an encounter, such as being hit by the lava-waves in OS. So that you can view your assessment when you join a different raid with them.
But all in all seems like a lot of work for a glorified Note system which is available to the default UI
This was only a suggestion and I was trying to throw some ideas around to help the general community which is what I believe the suggestion forums are intended for. However good or bad the idea maybe, constructive criticism is always helpful. Unfortunately in the internet community there will always be trolls like yourself.
It's an interesting problem, but with no deterministic algorithm to solve it.
I voted yes (skill > gear/achievements) in the poll, but that yes is conditional. I've been taking my Tree Druid into ToC 10/25 (normal only) even though he has Naxx25 gear with a few Ulduar and ToC pieces. Now, even though I can heal fairly well, I'm beginning to feel the limits of my awful gear (it's not my main toon, BTW). I'll never even try to step into Heroic-difficulty ToC 10/25 and I doubt he'll see the inside of Icecrown Citadel with his current access to gear.
In summary, I feel my "skilled" use of potions and cooldowns and my ability to not stand in fire helps to compensate for my current lack of good gear, but I'm at the limit now. My druid would likely answer "no" to the poll in patch 3.3.
Addons like GearScore only bother me in that they try to share their results using the addon channel, contributing to random disconnections during data-heavy raid encounters. Aside from that they are a tool for pre-made PUGs and my friends and guildies trust me when I volunteer to heal stuff.
Regarding addons that allow you to personally rate other players human-to-human, I don't know of any. However, I came across ZarkMark which is a website that collects these ratings. So if enough players use it then it would be a terrific service.