I don't know about file size since I don't upload videos/have a YouTube account, but it seems like YouTube uploaders can make their videos as long as they want now.
Personally, I think its kind of annoying as some people have greatly increased the lengths of their videos which means a slower or longer loading time for the viewers, or worse, the video will start buffering.
Not really, only some people have a 4 hour limit, while Partners and 2006-Directors don't have a length limit at all.
All the other users have 15:30 minutes.
Oh, no wonder I thought the time limit was removed, most people I watch have been partnered. I do remember some users having the time limit moving up to 15 minutes though.