My oldest DS did afternoon preschool and K - we loved it! No rushing around in the morning was the best part. We could sleep in or hang around the house in pjs until lunch, or we could get up and go do errands or something fun as a family. After lunch together my younger DS was ready for a nap, so we drove older DS to school, younger DS fell asleep in the car, transfered to the bed, and I had two hours to do what I wanted. It worked great for everyone.
Afternoon class was a bit more calm, plus there were only a couple afternoon classes versus many in the morning, so the whole school was emptier and quieter.
My younger DS is now in morning preschool (afternoon is not available here, we've moved) and I can NOT get into a good rhythm with my days.