I also work at a place that provides doggie daycare (also boarding and grooming). I have mixed feelings on it. For my own dogs, I would not. Mostly because I do not trust someone else who is not as familiar with my dogs to pick their play groups, and because I know that both of mine have the capacity to be dog-aggro. I will arrange one-on-one myself when the circumstances allow. I also know that dogs that come to daycare are not always perfect citizens, and I don't want my dogs picking up bad habits. I've seen dogs that come to daycare pick up things like leg hiking, neurotic weaving, barking, shredding toys, etc.
Generally speaking, I see some dogs that benefit from daycare, and others that you wonder why their owner insists on bringing them. Puppies benefit from well-organized playgroups, especially considering the other services we offer. (In other words, if a puppy is coming for their first groom/bath, we will see if they can play first. It makes our establishment less scary for them. Since our indoor pen doubles as the grooming area, they also get to see/hear things they wouldn't normally experience prior to being groomed.) But some dogs come to daycare and sit in the corner the whole time, completely ignoring the other dogs or even repelling them. Others come in growling and suspicious, and their owners insist that they are fabulous with other dogs. And God forbid you tell someone their 5-year-old intact male or unsocialized Pit Bull cannot play in the group.
I think doggie daycare is great for the right dog. If I had different dogs, I might use it.