I had lunch today at a local seafood restaurant and our waitress was great: she was engaging, attentive, and genuinely enthusiastic. The food was great too, but that's beside the point. Even if the food had been just okay I would still have rated the lunch as excellent just based on the great service.
Many customer service experiences lack enthusiasm, which is a shame. Showing some enthusiasm can be an easy and meaningful way for a customer service rep, sales person, or really anyone to delight their customer.