A week and a half ago, we purchased a big boy bed for Joel. We figured it was best to get him used to sleeping in it before the new baby arrives...and if it didn't work, we at least had a few more months to transition him. It took us two days to put it together (Ikea, how we loathe you and love you all at the same time). We purchased a bunk bed, but only put together the top bunk, with the rails around it to prevent Joel from falling out of bed. Joel enjoyed helping hammer it together.
A little play time, turns into a lot of playtime. He really doesn't want to get off the bed. He loves it too much. He actually has to show all his friends his new bed.
And yes, he does actually sleep in his bed. In fact, he does really well. It was barely a transition for him. The first few nights he woke up a bit scared, wondering where he was, but it was nothing a quick cuddle couldn't fix. He's slept through the night a few times already and has only really woken up due to extreme gas or teething pains (which is really normal for him). But mostly, he is excited to go "nigh, night" in his big boy bed.