M.A.
My daughter moved into a big bed when she was 3... we never used a toddler bed, just took the front rail off of her crib. So she went straight from that to full-size bed. We chose full-size b/c I want her to have more room later for sleep overs and in case her sister wants to sleep in there with her. I also wanted her to have something she can take with her when she leaves home (we bought her a nice whole bedroom set that I am hoping will last a very long time). She rolls around too like other people said so this way she has more room. We never used a rail either. She did fall off a few times, but she hasn't done it in a very long time. She learned quickly. :-)