Last weekend I just decided to convert Josiah's crib into a toddler bed. It says on the manual that you can do it as early as 18 months and since he is 19 months now I decided that now is a good of a time as any. Also, it is safer this way ultimately because if he tried to climb out of his crib he could really hurt himself because it would be a longer fall.
The second day we had this set up when he took a nap he accidentally rolled out of the bed onto the floor which woke him up with a start. He wasn't too pleased about that, but since then we have had no incidents. At night, we say, "Josiah, climb into your big boy bed," and he happily climbs up and grabs his blankie and blankie bear and goes to sleep. Sometimes when he is not ready for a nap time he will play in his room for a bit (he can't open doorknobs yet) but then soon after I put him in there it is silent, so I know he sleeps.