Have to agree with EmperorIng. I opted in on it, then opted out again. The only obvious difference that that the site is even more convoluted than before, and also bloated (probably to better "support" browsing the site from touch screen devices).
There's an inherent flaw I have here. I saw the feedback button on the left. But I didn't want to use the new interface enough so I could give proper feedback (Though I am not under the illusion that the Youtube crew ever listens to the feedback it gets).