Hi! So I've been using Mavericks on my Macbook Pro 2011 until a few days ago. I also played some graphically intensive games on Windows like Battlefield 3. Everything was always rock solid. These days, wanting to upgrade to Office 2016, I did a clean install of El Capitan public beta. The first fews days worked out ok, just a few glitches here and there. But today, the screen got some graphics corruption and the system locked up. Sadly, my main work laptop never booted any system again, not even Windows. I guess my Radeon HD6490M is gone! The only way I booted El Capitan again was by removing AMD kexts from Extensions system directory. So heed the warning, El Capitan may very well fry your gfx and kill your Mac.