I've been to Rainbow Garden for lunch several times. Each time I've left full and happy. They offer a very affordable lunch menu. Their portions aren't giant sized either, so I don't have to worry about taking home a smelly box of Chinese food.
The staff can be a bit aloof at times, but they're usually really busy around the lunch hour. The atmosphere has gotten better over time as they've opened up more of the floor plan and made it more accommodating for the larger crowds that come around the lunch hour.