My main problem with iCloud is that when I first started using Apple products, I used my own email address as my Apple ID. Later I registered a separate Apple ID with my desired username @icloud.com when they became free, but before it was possible to create an @icloud.com address on your existing Apple ID. Now it's impossible to merge these two and I don't really want to dig myself into a deeper hole by creating some randomword@icloud.com on my primary Apple ID just to be able to use the iCloud+ custom domain feature.