This new alpha is so laggy, when i am in champ select i can barely change my masteries. If someone dodges and the queue pops instantly after that i can't accept. So i am just hoping for there to be a way to go back to the legacy client once the new one comes out fully.
THANK YOU. I absolutely agree. I have the same issue, but fortunately I do have (barely) enough time to do what I need to do -- select / ban champions, change masteries (but it lags too much to change up my masteries as needed in the Lobby), and accept Queue.
STILL, this is a big issue, and since it's just the client and not the game itself, I hope that over time it will be optimized for everyone's settings, instead of being forced to use the Legacy Client.
bump
Really though, the Alpha is so beautiful I don't want to be forced to change to Legacy Client because of some frame-rate or otherwise lag. 
I absolutely agree. So much lag, i can't even to lock in.
i cant change my masteries at all wtf is with this new client
