Seconded. Married to a teacher who is now running daycare for some friends' kids so she can stay home with ours. I'm a tech for local catholic schools whose teachers and staff can't deal with Linux though I myself have been a user for more than a decade.
We have acquired some older P4 machines and I have one slightly newer one that I set up as an Edubuntu LTSP server. The older ones NetBoot from it.
Point is, my 3-yr-old and her friends between 3 and 4 love Gcompris, and my wife thinks it's incredible. Connect-the-dots, memory, typing blaster and even a simple mouse-learning game where one wipes translucent bricks away to reveal a fun animal picture. It gets used for maybe an hour total per day, so it's a fun reward for good behavior and a pastime while the babies need feeding or lunch prepared or laundry done, not a mindless zombie creator. Compare the activities with what's playing on the Disney or nick channels and you can easily see which is better for a developing mind. Most activities are nearly if not entirely on par with the sensory and craft activities my wife plans with the kids, though visits to the rec center are a nice break from monotony, and they also attend a nursery school 2 days a week. Nice days are also used well with play on the swings and trampoline. I'm just saying by way of comparison for the benefit of those commenters who will say, "why stick your kid in front of a screen?" As though life is binary.