Our toddler has been upgraded to a big boy bed as of February 1st. I was a little nervous about it because I wasn't sure what he would do about it.
For a few months now he has taken weekly naps at my parent's house on a mattress on the floor. Not once has he fallen out. He was escaping right away or locking himself in, but that was solved with my mom's old trick of wedging the door shut with a wash cloth.
My husband and I decided to upgrade to a king size bed and give out queen size to our big boy. We put everything on the floor and he was pretty cool about it. He went down for bed three nights in a row without protest, complaint, or hopping in and out of bed. In the morning he hopped out of bed and let himself out. He went down for his afternoon nap the same as always and except for one instance of playing with the light switch, he took a nap.
No falling out of bed yet and only one nighttime waking. I'm so thankful he's doing so well.