I just checked the App Store to see how El Capitan was doing: 5 star ratings: 69 1 star ratings: 115 That's even worse than Yosemite. My personal experiences are bottlenecks and excessive resource consumption to the point that the system almost locks up. It would be nice if I was doing anything significant, but basic web browsing and checking e-mail doesn't cut it. The culprit for me appears to UserEventAgent. I found the following quote interesting: "Software developers and users have argued that Apple's yearly release schedule and development practices have compromised stability, and meant that no version of OS X is truly recommendable for users requiring reliability above new user interface design and features." Source: https://en.wikipedia.org/wiki/OS_X_Yosemite El Capitan functions like a beta release.