Whenever you change something, it should be for the better. Steve Jobs was notorious for this. People fell in love with something that managed to stay cutting edge continuously for a long period of time.
Rolling out updates for phones and webpages is hard to do, mainly because when you have developers work with their products, they do not have a homogenized setup that is congruent to what all of the customers/clients will be using, neither can they replicate the traffic and heavy usage that their program or update will attempt to sustain when it is released.
That being said, simple visual cues and button/program functionality is something you CAN test.
That being said, the new layout YouTube has chosen is a mystery. A clean layout is not akin to empty space. Even taking basic entry design classes teach you how to justify your content to different sized screens. No one at YouTube has taken these classes. But maybe one day.
That being said, thank you RT Productions/Staff/Ben/Everyone involved for keeping your site mostly functional even in the early stages. There have been many hiccups, but when you build from the ground up, you will hit a few roadblocks.