Hi R.
I too, had to move an 18month old to a toddler bed. I too, was critisized for it. She is to small, to young, bla, bla, bla.
I had to do it for her own safty. She is like a little monkey, climbing everything, and climbed out of her crib twice.
My daughter also an excellent sleeper at night, became a night waker, every couple of hours, standing in the middle of her room crying. To solve this, I moved her toddler bed into my bedroom until she became used to the new bed. When she would wake up, I would asure her that I was there for her, lay her back down and she would return to sleep. And once she started sleeping through the night again, I moved the bed back into her room. She slept more comfortably then. I will admit, there were a couple of nights, when she would wake up. Just go into her room, reasure her that you are there for her, and return her to her bed. My daughter is 2 and a half now, and all is well. I wish you the best of luck! Dont let all the negative critism get you down! Feel free to email me if you have any questions. Heidi