I have voted the same as yourself, I believe it feels quite closed off with comments being on a tab which people will have to choose to click on to read which could mean channel comments will completely drop in amount and I dont think the channel owner will check them as much although I think it will have a positive effect on YouTube spam and I think it will slow down sub 4 sub and such quite a bit but I believe sub 4 sub will always have its place on there. It does look the part, I just think it would be best if they applied the new look over the current one so its more modern. I do agree with you about the autoplay feature, if that isnt included peoples video views will drop a lot and I think so will Googles/YouTubes revenue for example, I land on an autoplay channel, the advertisement runs automatically too and I may choose to view the adverts website, without autoplay I may not have bothered to 1 view the video for all kinds of reasons, maybe the thumbnail wasnt very appealing meaning I was missing out on a good video and 2 click see their advertisement and 3 click the advertisement, I believe autoplay is almost crucial to YouTube.
I suppose YouTube could get rid of it but it will have a massive effect on a lot of important parts of YouTube.
In Cosmic Panda I would like to see more styling options such as transparency and editing colours of text/links like usual but other than those things I think it looks good and works well. That's my overall verdict on it.