Does using it require Google Plus?
If you were to start a hangout via Gmail from your Google Apps account, you get a dumbed down version that doesn't support features like screensharing and up to 15 people.
You would need to use an account that has G+ connected and start the hangout from the hangouts app or from G+. So I think yes, you would need a G+ account to use this unless Google changes that.
So not really sure what awful problems you expect to pick up.
I love Google Apps, don't get me wrong, but it wouldn't be fitting in my current environment. :-)
(We might just be able to set up "dummy" accounts that nobody ever notices or deals with directly; still very intrigued by this)
In a more technically-savvy organization, I'd definitely just integrate more closely with Google Apps and be happy.