I'm running on a 2012 Mac Mini Core i7 with 16GB of ram with a spinning rust hard drive.
El Capitan has sped up the OS for me compared to the previous OS X release. Yosemite was so bad that I found myself avoiding using my Mac Mini instead using my rMBP with an SSD because the Mac Mini just felt so incredibly slow. With El Capitan they feel similar to me. Certain disk operations of course are slower, but overall the usability has increased under El Capitan versus Yosemite.
Based upon informal replies on Twitter when I posted about my upgrade experience, I wasn't the only one that noticed a distinct speedup compared to Yosemite on older hardware.
Mid-2012 MBP with 2.5 Ghz i5, 4GB ram here. I thought Mavericks sped it up, but Yosemite is unnoticeable. I couldn't tell you if it is faster or slower than when I bought it, to be honest. All the problems people mention in the thread, I'm somewhat surprised by. I guess I'm lucky enough to not have wifi issues, rely on iTunes, or Apple Music.
Until six months ago I did most of my day-to-day web browsing on a 2007 MBP with a 7200 RPM 160GB drive. I had to upgrade because the dying GPU was destabilizing the system, but with 4GB of RAM and competent ad-blocking, it was fine for the light use it was getting, and that did include Spotlight searches.
This is my experience. I have a late 2013 iMac with a spinner running El Capitan and it's one of the absolute worst OS experiences I've ever had and I've been using computers since the 80s.
