My dog goes to day care occassionally and she loves it. She has several "friends" that she has made there. It is really great for her because she is still very young and there are lots of other young dogs who like to play as much as she does. She comes home exhausted because she plays the whole day and is really mellow for the next day. We work and she has a dog walker that comes on the days that we don't take her. The only drawback is that when she leaves can smell pretty strongly of dog odors.
There are a few things to keep in mind. First, make sure that you pick a reputable place. I have heard of some dogs getting hurt at daycare. Make sure that the one you pick screens the dogs beforehand and makes sure that they get along with other dogs. It is important that they screen out the unsocial and violent dogs and that they have adequate staff in with the dogs at all times to prevent fights. Also, we picked a place that has separate spaces for the big dogs and small dogs since we were worried that our small dog could get hurt if she was in with a bunch of much larger dogs.
I take my furbaby to doggie daycare a couple of times a week, and she loves it! I have a 3 year old lab, and it gives her an opportunity to play, interact with other dogs and be a part of a "pack". (She even has a boyfriend there named Gus!). When I was researching daycares, I scoured the internet, asked co-workers and neighbors, and toured the facilities prior to dropping her off. Make sure if they provide outside playtime there is a staffmember outside with the dogs at all time, and make sure to find a place that is dilligent about your pets safety (the first thing they should ask for from you is your pets medical/shot records, I also like that my daycare has seperate play areas for different sized dogs!). I just love my daycare (barking hounds in atlanta) they even give me updates as to how she's going throughout the day (I called a LOT when I first started sending her!!)