That's what I do too, and you can also add it to your home screen.I don't know I watch HQ youtube videos by going to m.youtube.com in safari and pushing the little HQ button.
Then click play and it loads in the youtube app and looks great (like wifi).
Honestly new to all this jailbreaking thing so thats about all the info I can give you.
oh I get what your saying.. that is annoying. I wish the youtube app just had a setting, low / high..I know about the YouTube web page with HQ. What I say is when I read something on a website that has a video, I want to watch the video in HQ without leaving the page and go to YouTube site.
But when you're on Safari and you read a page with a video, you don't know what the title of the video is to search on YouTube. And you have to leave the web page.It's a bug with My3G with Youtube app at the moment.
However, a piece of advice from me is that Youtube Mobile WebApp is a much superior place to browse youtube. And you just need to click HQ to force it to go HQ even on 3G
I haven't used the native Youtube app in quite a while now
And again unfortunately My3G has Youtube app bug at the moment. Your real option for now is to use 3G unrestrictor and uninstall my3GBut when you're on Safari and you read a page with a video, you don't know what the title of the video is to search on YouTube. And you have to leave the web page.