You know, I was totally opposed to full day when out district initially changed. I was ready to go private until DS's preschool teachers (who were just wonderful) were cheering that the kindies were going full day. As it turns out, we ended up really liking the full day though. Kindergarten feels more like kindergarten now. DD's day was 3 hours crammed full of curriculum and they had little time for anything else. DS actually had time to PLAY. DS had 3 recesses and a lunch. They had daily arts and crafts time. They had time to do fun science experiments, build with legos, rehearse school plays, go on fieldtrips, have special guests come to class, go to the library, ect. They did just as much curriculum but it was spread out in little bits throughout the day. DD really hated kindie and DS loved it even though his days were longer.
I don't know that full day kids are better prepared. Like I said, they did the same math and language arts curriculum. Kindie was just more fun full day and they had a chance to learn OTHER things too.