I jump regularly from 6 pack to Garmin glass, and absolutely love the glass. Workload plummets, enjoyment goes up, and I find everything is very intuitive...
The IAS tape is very well set out (on the G500 for my mind) and I get so much more useful, timely and easily assimilated information from it that it's backup in the corner. The 'black box' confusion, I think, comes from over thinking it. Just because it displays red X's over it, doesn't mean it's failed, you should just be going through your IA's like you would anything else. The black box can't make your bricks (indication) without clay (air data). It's just if the weak link in the left hand seat is competent, current and familiar with their equipment, failures should be treated like any other system failure.