She was 16mths (i think). NO real problem transition wise, and she loves loves loves her bed and has no problems going to bed/sleep if she is tired (takes herself off to bed herself now). She is certainly happier in a bed and it's easier for me to comfort her.
Naps have improved (she has 1hour and half now) and self-settles.
Tbh things are the same if not slightly better than in cot - if she wakes and needs me, she either cries and I go to her or she gets out and comes to us (she would have cried in cot and I would have gone to her) so works for us because we don't leave her iykwim - would have been a pain if we were CIO people . She is def happier being left in her bed than cot (we changed her in a bed because we thought she might like the independence/control of feeling she *could come and get us) and would rather sleep in her bed now than with me - we were co-sleeping a lot.