Edit: As a lot of people seem not to be reading the blog, I'm going to clear up the most common misconception first. I play Yasuo, he is a lot of fun, you should try it. I don't need any advice on how to counter him.
I'm a player who has always played to within a sliver of my power in toplane. What I mean is, I'm as aggressive as I can possibly be without dying. This generally means I ward up and go full offense on the enemy, going for kills while paying less attention to CS as I could be. This means I'll usually (60% of the time) be leaving lane something like 3/1/2, but be down 15% of the CS as my other laners. This is a playstyle I'm very comfortable with.
But Yasuo, whew.
There isn't a single other champion in the game who I feel it's actually worth ignoring the other laner and getting perfect CS with. On paper and in game, he scales so much harder than anything anybody else has to offer. I could pick Tryndamere, and when I do, I play him very well, but why would I pick him when I have Yasuo, who does more damage and has more crowd control and blah blah blah.
My point is, Yasuo represents a new paradigm for my play, and for the game in general. I really think Yasuo is going to be picked up by the pros, since he is so good with gold and the pro scene is so passive in lane in general, he is going to be making all of the money he could possibly be making, and carving up mages and tanks alike by 30 minutes. His damage is ludicrous, his lategame is unparalelled. His shield is incredibly hard to play against. His poke and sustain once he has Shiv is abusive.
He has weaknesses. A soloq team which does not pack many Airborne crowd controls will be more difficult to play Yasuo with, but NOT impossible or ineffectively. I feel like being able to activate R off of other's crowd controls is icing on the cake, not an all-important part of his kit.
Similar to Pantheon, he is able to function in lane and lategame without his ultimate. Since that ArPen only works on bonus armor, it is primarily going to be useful when attacking super-tank champs like Shen, Malphite, or Rammus that have been knocked up somehow. It's not going to be as noticable on other champions until they pick up their Zhonyas or GA. It's worth mentioning that a 30-minute Yasuo is able to proc his knockup from 0 stacks in about 3.5 seconds.
A lot of people are responding that you should simply "Poke him down" but I find that to be far less effective against Windman than a lot of other champions. His shield can be charged very rapidly by dashing through minions, or slower by just walking around. A targetted spell like Teemo's Q can just be Wind Walled on occasion. His autoattack range is essentially 475 making it very easy for him to last-hit even at large distances, meaning the enemy may have to get right up into your minions to hit you. After he gets a Vamp Scepter and is able to sustain his HP as well as fend off poke, it's very hard to get him out of lane. Yasuo is tremendously resistant to poke.
To finish: Yasuo IS overpowered when played a certain way. The fact that he's manaless and has a free shield makes him incredibly difficult to kill in lane (Read: Riven, Renekton, Shen), and the fact that he uses gold better than almost anybody means that if you're going even with Yasuo in lane, you're actually losing.
He's a god.
Play him before he gets a nerf and experience the golden age of the new toplane critmaster.