I don't know- it probably depends on the couple. Toys can certainly spice things up, but they are just window dressing. If you don't have a solid relationship based on respect and trust with good communication thrown in, toys aren't going to help.
OTOH, toys can add another dimension of fun and intimacy to a couple with a solid relationship.
I know this is a toy site so this might be heresy here. But a lot can be said about the couple who know each other well enough to have magicically, fulfilling, intense sex without any toys at all. (Not everytime of course- I'm not crazy!)