we switched at the end of April when we moved into our new house. we talked up his big boy room for a while and pointed it out every time we were in the house while we were working on it.
the day we moved, we set up his room with a new chair, bookcase and books, open closet with clothes/bins/etc. and his bed plus his old crib. we let him choose where he wanted to sleep and without hesitation he chose his new (froggie) bed. he never wanted to sleep in the crib again.
since April, he has gotten out of his bed on his own once. he figured out after a while that he could get out, but he just doesn't. so we have no gate or anything in his room. when he's ready to get up, he calls "Dadda" and we come get him. sometime he has toys in there but that still doesn't entice him to get out. we got really lucky with that.