There was about 3500 people loggeg in YR Client today and I have noticed a greatly increased CPU usage of my YR Client. One whole core of my (not very strong) processor was fully loaded and I was experiencing lag in YR Client. I dont think rendering GUI is a problem, because:
I have tried other GUI renderers in options and nothing changed.
I have tried to decrease GUI resolution down to 800x600px and problem was still there.
CPU usage only increases after I press "Play Online" button and players/games lists starting to emerge.
I suppose there is something wrong with enumeration of those lists in source code of YR Client...