One-piece apron+shooter gauge.
DCS sound board. Some of us do not, in fact, think it was superior. Audio designers included.
Plastic GI insert panel behind translite.
Dropping the display panels with game-specific artwork in favor of generic molded plastic panel.
IMHO the old ball trough (with two coils, mechanical switches, and typically 3 balls max) had less reliability issues.
Launch button instead of manual plunger.