We're going to switch my son soon as well. Here is what I expect, based on what my friends have told me. He will repeatedly get out of bed, either to play in his room or to come find you. A gate on the door will work wonders in confining him in his room, but prepared in the beginning for him to stand at the gate and cry for you (this should stop within a couple of days if you make it clear that you won't be getting him out). He very well may sleep on the floor, or even right next to the gate. This too will stop after awhile as he learns to like the bed more. It usually takes about 3-7 days. Naps are tough too.
I'll be going through it within the next three months (possibly very soon), so I'll feel your pain!
A friend of mine just did it two days ago. If you want to ask her about it, you can post your question on http://oc.citymommy.com and she will reply!
K. : )