He looks very much like Lee Sin in that he gets abilities after he's used his first ones AND that he uses Energy. However, he looks quite interesting as a character...
Passive: Interesting... So he can gain an extra 25 movement speed? All in all, I'd say increase this just a bit... Maybe 6 or 7 movement speed per stack? Although, with an AS of 2.5, you can have the MS within 2 seconds... But its a nice ability for early game, though it doesn't really fit with his assassin role - he can't use that movement speed to get in quickly, and if he stuffs up, he can't catch up to them quickly with the bonus speed.
Q: Are his scaling stats going off bonus AD or base AD? Otherwise, this is a good ability, the base damage is good, but the scaling is pretty low. At the moment, he's very non-item dependent - I'm not sure if that's what you were going for or not - but he could stack Phantom Dancers and still do a tonne of damage. I'd decrease the base damage and increase the scaling. This will make him more like other assassin types - weak early game, but powerful late game. With the way you have it now, it looks like it would be a strong early, and steady mid game, but a bit weaker than usual in late game.
W: A pretty good ability, a shield with two counterattacks... Can't really say much about this one, it looks pretty good. However... 2 and 4 seconds are fairly long timers in LoL and the opponent could get out of range in that time - will the two blows still connect if they run away?
E: This move is pretty much his W with a slow. Hence, I don't like it that much. It looks like it should be his prime move, his really nukey strike. However, it does about the same amount of base damage, and has less scaling this his W. I'd scale this up a bit more.
R: I don't understand what is meant by 'available at level 1' and 'does not require a skill point'. That seems rather odd... I think you should have a more assassin-y style ultimate, or add somehting that makes it slightly more useful - such as increasing the needed-cast-time of the 2 second effects by a further 2 seconds AND giving him full passive stacks for a period of time.
In any case, he looks like a fairly good champion.