In-Game XMB is useless
In game music? MP3 Player... get one.
In game message sending? Phone... get one
In game web browser? Laptop... get one
In game YouTube? Useless, eat it
The only useful "In game feature" would be the ability to stream what you are playing and have other people join in and watch. If this is a co-op game, they could watch, jump in when you get to a hard part, kill the enemy, jump out.
Though this can already be achieved... webcam... get one.
You guys are delusional if you think that In Game XMB will solve any problems. If anything it will just make you more aware of the flaws. That being said, In Game XMB won't hurt anyone certainly and has been requested alot... but, you guys will understand soon enough.