Give it a go, you still have the cot set up so you can move him back if it doesn't work out.

My DS went into a bed at 18 months of age and it was the first time he ever slept through the night, it was a huge success for us. He still was in his sleeping bag for a little while but we eventually transitioned him out of that. We just had removable bed rails (from Target) either side of the bed, but interestingly he was never as much of a wriggler as he was in the cot once he was in the bed. I think having a pillow helped. We moved him because his night sleep was so bad we didn't think it could get much worse and in the end we wished we'd done it earlier!

We have just moved my DD into a bed this week, she is 15 months old next week. We need the cot for the next one, but she also was not sleeping well at night after previously being fantastic so we thought we'd just try it. Another success story, she slept beautifully all night after only waking up once after a couple of hours, a bit disoriented - so I thought I'd try her with her new pillow because DS took to his straight away - and sure enough, she snuggled down and slept for the rest of the night - we'd started her off flat on the mattress. Once again with her we are keeping her in her sleeping bag for a while so that part of her sleep routine remains the same. And once again we are seeing that she is not moving around around in the bed the same way she moved around in the cot...so I am sticking to my theory that the pillow helps.

It is taking a bit longer to settle her off to sleep at night but not excessively so, we figure this is a temporary thing while she gets used to bed. She loooves it though, she is always going into her room and climbing up and sitting on the bed and bouncing around on it. It's just like going away on holidays, they need a few days to get used to the new surroundings.