Xander's still doing really well with his big boy bed. He loves it! He's slept in it every night and I've only put him back in his crib for one nap in a week and a half. That day I knew he wasn't going to sleep but I needed a few minutes to get some things done and I had no way to keep him in his room. As of Saturday, we now have that worked out. We bought child-proof door knob covers and attached them to the inside of his doors (he has two).
On Saturday I worked and David had Xander. David had put Xander down for a nap when I called to check on them. David said he couldn't hear Xander and figured he must've fallen asleep. After we got off the phone David went to check on him. He found him driving his toy car in our bedroom! Apparently he decided he didn't need a nap and would rather play in Mommy and Daddy's room, his favorite place to play. :)
Thankfully he hasn't figured out the door knob system - either how to work it or how to take them off. I give that about 6 more months, but by then hopefully he'll be a little more obedient about staying in his room.
On Monday night, for the first time, he asked to sleep in his crib. (We're not taking it down since we're going to use it for the new baby in the same room and move Xander to his new room.) I explained to him that the crib is for babies and his big boy bed is for big boys like him. That satisfied him and he didn't want to sleep in the crib anymore. I personally think it was his way of making excuses to stay up a little longer. He's getting pretty good at that, too. :)