Just as to comment, on the 536 build, I hard reset because of the "Loading..." loop; didn't help...at all. Still got it and it was random. I could go a day without it happening, then the next it would happen every time I unlocked the phone. If it's the only problem you are really dealing with, I wouldn't bother with the hard reset. I sure hope MS gets the updating process fixed. When the average consumer gets the Update notice, and the phone gets updated, it needs to be seamless for them. Otherwise, it'll be a mess. Just to add, when the loading loop would keep happening and not go away no matter how many apps or other things I tried to load or use, one thing that worked 90% of the time was to load Cortana and tell her "fix my start screen". I'm not kidding either. Sometimes she would misinterpret as "Text my start screen" and that would never work. Kind of funny when you think about it.
I'm downloading this update now, as I had to go back to 8.1 from 10536 due to the phone getting very unresponsive at times and the camera started displaying "Saving..." almost all of the time and was messing with my picture taking. Not nice. I'm encouraged that a lot of folks here are having a pretty good experience overall with the 549 build. I'll see for myself tomorrow.