Just installed Windows 10 on my 21.5" iMac (HDD based, no SSD). It flies like a rocket, everything is literately instant; from opening apps to general actions. I'm not even running on an SSD Mac, and this feels faster on my HDD than Yosemite does on an SSD Macbook! I upgraded from 8.1, and this feels a lot faster than 8.1 as well. Does El Cap feel more like Windows 10 in terms of a responsiveness standpoint? Because Windows 10 is just silly fast and I would say that it feels more responsive than Yosemite.