Gizmodo posted an article last week about this experiment. It turns out that YouTube will soon launch this new interface.
Another change is that YouTube preloads the page and the first part of the video you're likely to watch next before you even click it, so that the video loads almost instantly. This works because the Flash player now uses adaptive streaming and downloads videos in slices. The first slice of the next video you're likely to watch is prefetched. This works well for playlists and search results (YouTube prefetches the first result), but also for video pages, where YouTube shows suggestions.
YouTube hopes to reduce the time between clicking a video and playing the video to less 200 milliseconds, which is what the human mind can perceive as a delay. That means instant video playing (if you ignore video ads).