I have to agree with Stacey. We had left the cot up in Sam's room after being advised it was the nicer way to do it. It was a disaster. She loved being in her cot so of course would rather be in there than the big bed!
Once the cot was taken away she only had a couple of bad nights and then was fine.
In fact now she loves her big bed so much and actually asks for bedtime
The other thing we did was attached the cot bumper to the wall beside the bed and put her toys etc in the same positions they were in her cot. I think that helped her transtition alot to be honest.
Good Luck.