I signed up for the subscription a couple of months ago, after using Lightroom 5 with no problems for years. From the moment I first starting using the new program, I noticed an enormous slowdown from the previous version. Everything is slower: the time it takes to open Lightroom & load images; the time it takes to execute corrections & spot images using brushes; and just generally toggling between functions. The brushes are less exact than they used to be and seem to have a lag + imprecise positioning. Images generally take longer to load. I am on an iMac running El Capitan 10.11.4.