Well, confusion aside, I like some aspects of the new pages. When there are lots of comments, I think the page looks a lot cleaner and it's easier to find related videos along the side because you aren't restricted by scrollbars and a billion categories. (Actually, I think the categories along the side are the same as always but there's more space for them so it's easier to look through them.)
But with no comments on the page, it looks really, really empty. D: There aren't enough lines on the page to direct your attention and it's just very hard for your eyes to make their way down the page. Actually, even with a full page of comments (so that it goes into pagination), the comments still don't go down far enough to match most of the related videos so you're still left with way too much blank space. :(
The design definitely needs more lines. There's waaaay too much empty space and I don't like that. Nor do I like the location of the description. D: I do like some of the new buttons they added, but overall it's just... the good things about it don't really outweigh the bad. D: I'm a big fan of redesigns on the web, normally, but this one just seems like they started redesigning the page and got a bunch of ideas for it, but instead of integrating them and making the page the best it can be, they just kind of half-assed it and stopped in the middle saying "Well, this is good enough." It just looks very unfinished.
Also I doubt this is April Fools since, like I said before, I've seen this layout for at least a week now. :/