Metro is intrusive? Your inexperience with Windows 8 is showing. If you're using the desktop, you'll likely only ever see the Start screen for a couple minutes in several hours of PC use. Even then, for most purposes, it works exactly like Windows 7 and Vista. Hit windows key->start typing to the first couple characters of the program you want->hit enter. You don't ever need to use the tiles unless you have some urgent need to use non-desktop apps. Even things like the classic control panel are still there and are easily accessible via a large shortcut on the the "Computer" section of Explorer.
Unless they're coming from Windows XP, almost all the behaviors from programs they know and love should work exactly like they did in Windows Vista and 7.