> Allows users to download videos from YouTube
That was pretty cool, but I honestly don't need that. I can already download any video from anywhere online using Google Chrome and the curl trick.
> Prevents the display of advertisements in YouTube video playbacks
I never saw ads on the mobile web version of YouTube, but this could be a problem when Google wants to insert them.
> Plays videos that our partners have restricted from playback on certain platforms (e.g., mobile devices with limited feature sets)
This was great! I actually remember trying to play a video that worked on my laptop and failed on my phone. I just went back to that same video and it worked.
The overall mobile web experience of YouTube is terrible on my Windows phone (and on my iPhone). Since most of you guys are probably iPhone users here is an analogy. It's like trying to switch from a native iOS maps (Apple or Google made) client, to Googles web version of maps. Yeah it works and does everything, but the performance is crap compared to the native mobile application.