We just moved our 18 month old into a "big boy bed" as he had been climbing out of his crib for about a week. He actually has one of those convertible cribs, so we just took the front off.
It went extremely well. It will be a week tomorrow.
We just kept the same routine for his naps and bedtime. We made sure all the same items were in his bed as were in his crib.
The first night or two he would get up so we went in to lay him back into his bed. We only had to go in one time. One nap, he took on the floor for about 2 hours.
But otherwise...it's going great. Cross your fingers!!! Only downfall is that he is not sleeping in as long as before (about 30 minutes) earlier. He gets out of bed to play around in his room.
HTH!