We moved our son to a bed at about 22 months. He loved it and felt like he was a big boy. We did tell him, however, that if he got up too many times, he would have to go back to sleeping in the crib. We also took out the frame of the bed, cushioned the floor and put a pillow right next to the bed so if he does fall off the bed, it won't be far and would be soft.
In addition, I got a digital clock that had big numbers on it. I covered the minutes side so all he could see was the hour number. Then I made a big number 7 and a big number 8 that was could take to the clock. On weekdays, I tape the big number 7 to the clock, on weekends, I tape the big number 8 to the clock. We told him that he could not leave his room until the numbers match. Once the numbers match, his prize is that he can come into our room and snuggle in bed with us.
We only had to put him back in the crib twice. He got up in the middle of the night and started walking around the house, so we put him back in his crib for the rest of the night. In the morning we explained to him why he had to go back in the crib and that night, we remind him of the rules and ask him which bed he wanted to sleep in. Of course he always chose the big bed, but as long as we were consistent the 2 times he tested us, he learned he had to follow the rules.
He did great with that and he'll be 3 next week. We do hear him playing in his room at odd times of the night sometimes, but at least we know he is there and is safe. However, as soon as that clock turns to the right number, you can count on him coming into our room at any moment.