DD went in a bed at 19 months. She threw herself out of her cot one day (she did have tonsillitus at the time so was clearly feeling super rotten) and so we put her to sleep in a travel cot as it was higher. After a few weeks we decided that this wasn't a good enough long term option so we put her in a bed.
She's been in one for about 6 weeks now and hasn't attempted to climb out once! She is the 3rd child though and does like to be treated like the older children.
She's in one of the extendable Ikea ones which is pretty low to the floor and quite small (before extending it). She's in a Grobag too.
I think it really depends on the child. We got a big girls bed for dd when she was just over 18 months as we knew handing over the cot to the new arrival due a few months later might be a prob, plus she was starting to try to climb out. Also she was starting to ask for a pillow like us and was refusing to wear her gro-bags anymore. We had a few evenings hassle until the novelty of getting in and out wore off but no real probs. I would recomend buying a wee step to go at the end of the bed to make it easy to get in and out and a bed guard. Now have number3 due at Christmas and have bought a crib so ds can stay in cot for longer - he will just about be 18 months when baby arrives. He just feels younger and less independant at this age than dd did and the move to a bed at this point feels too early for him. Go with your gut i reckon.
Advice if you decide to go ahead, def do a bed guard even if you think not needed - our dd never slept up to the cot bars so we assumed she may not need one and she fell out at some crazy time am the first night - we lost guard just after she turned two but she did def need it initially - tomy one is good, dd loved the fact it had a pocket to put things in and could tuck books down the side. When buying duvet don't get more than a 7tog or child will boil and it will be very heavy for them to move about etc - goes without saying make sure duvet and pillows are washer/tumbler friendly. HTH