Perhaps I can assist. My GF upgraded her MBP to El Capitan. Told her not to, but who am I tell her what to do... ;-)
Ever since, this is the new situation:
- Her MacBook doesn't go to sleep. Ever. It will suspend to disk, yes. But then it takes about a minute or more to wake back up. Sleep though it will not. Unfixed by Apple. Yes, there ARE a couple of SUDO-terminal commands that claim to solve the situation for one person or another, but really now?
- "Exposé" takes literally 3 seconds to comply on a cluttered screen with many windows. Not always, but very often. I reboot and it's gone...for a while. But it comes back...Really now? Frequent reboots?
- El Cap eats her RAM for breakfast. More that 2 GB on a idle desktop. For what? If the OS offloads into RAM to speed things up, I would be fine. But it doesn't.
- Disk Utility used to be a swiss army knife that I LOVED to use to mount, modify or create images of the most broken, non-standard volume or disks in SL. As of El Capitan, its ABSOLUTELY useless. Yes, I am aware that there are SUDO DISKUTIL - terminal commands... But really now?
I had it. Wasn't aware of it until it happened. Very, very bad, first hand experience. But when I recall correctly, it was fixed, wasn't it?