I've still got your second problem. I'm really disappointed with Apple about this as they appear to have made no effort to fix it.
Every time I sync an iDevice with iTunes, all the artwork disappears off the iDevice and then it slowly re-downloads, although there always ends up with some missing - but different ones missing each time.
I can only hope that the reason it hasn't been fixed is that the fix is so major that Apple have decided to completely re-write the code for iOS 6.
What makes it all the more annoying is that this is a paid-for service.