I don't like them.
They look cool, at first, or so I thought when they began testing them a while back. But upon using them, I felt like they were much less 'user friendly' than the original design. It's possible I'll get used to it. Maybe. The lost of the 'Video Log' feature is particularly bothersome. As many know, my 'Talented Girls' playlist was used as my Video Log, and it had a place of prominence on my channel page. Now it's just another playlist.
UPDATE: Still a little buggy, YouTube. I see issues with the video thumbnails overlapping in some cases on the grid view. Also, the 'Most Viewed' feature isn't arranging the videos in the proper order.