I love Youtube, for what I use it for!!!. I have learned so much more about music, and I've been able to really explore it some depth.
One area of music I've always needed to know more about is the classical side. Using youtube, I have been able to research the `masters' and see all their symphonies performed all around the world, as well as modern and minimalist interpreatations (such as Vanessa mae's version of vivadli's four seasons- that sort of thing).
But I've learned a lot more tan that, and realy enjoy seeing old clips of songs I liked years ago, but never saw before.
The other think i like about it is beng used by animators now and film students now, and i've been able to follow the final works from some the good schools around the world. Its really interesting to me.
I never come across the stupid stuff, but I don't search or browse that stuff.
Its like the net, really- it full of porn, and worse, but I wouldn't `write it off' because of that.