We had to put Bub into his big boy bed to get ready for this big upcoming moving adventure. It's a total bitter sweet transition for me -- part of me was so excited to take that rail down so he could be a big boy and come and go from his bed as he pleases, and a part of me wishes I could leave that rail up forever. He is my baby after-all...:)
I didn't move my daughter into her toddler bed until she was about 2 1/2 years old, when she started climbing out of it (which is the usual transition time depending on your situation, I think.) We couldn't wait till 2 1/2 years with him. He doesn't fit in a pack-and-play anymore and it didn't make sense to lug his entire crib to Seattle for a month. This way he will be used to the freedom of his toddler bed before we visit Seattle.
The fun part about having all this freedom is you don't necessarily have to sleep in your bed if you don't want too. The carpet works just fine. :)