I have latest chrome canary and Im trying to watch a 4k resolution video on youtube but its really laggy. Im using 13 mbp 2.4 c2d, 320m graphics card on osx lion. Could it be that my cpu is too slow?
4k? Are you sure? Isn't that a bit big for any screen to display anyway? I wouldn't be surprised if a Flash video wouldn't support that size correctly, especially considering how CPU hungry Flash is even if the video is tiny. I think it's quite normal if it's laggy, regardless of your hardware. Sometimes software can be so bad it doesn't really matter what computer you're running it on.
It is neither about Lion, nor canary. I have SL and chrome 13 right now and 4k videos are extremely laggy on youtube, even on quicktime and vlc. My processor is slower than yours though.