I've experienced the same performance issues with the Flash plugin on OS X. I use the iStat menus to keep a tab on my CPU usage, RAM usage and system temperatur

I've experienced the same performance issues with the Flash plugin on OS X. I use the iStat menus to keep a tab on my CPU usage, RAM usage and system temperature. Browsing the web takes very little CPU, and there are spikes in CPU usage only when I open a new page and the browser tries to render it. Just reading a webpage takes no CPU, as expected. Temperature remains in the range of 35 to 45 degrees Celsius. Enter Flash. CPU usage oscillates rapidly between 0% and 30%, sometimes even going upto 70%. The temperature rises to 70 degrees Celsius. This problem is not just Mac-related. I've experienced high CPU usage even on my Linux PC. IMHO, Flash is pure evil.