My daughter is 19 months old and has been hating her crib since she was about a year old. She is super active at night and kept hitting her head on the crib rails and waking up CONSTANTLY.
About 2 months ago, I switched her over to a twin mattress on the floor with side rails surrounding it so that it was still like a crib, but she could crawl out of a space I left with the side rails. I place a pillow in that spot just in case she pushes herself out off the mattress in her sleep. Since then, she has been sleeping through the night (for the most part) and in the morning, she can get out and play until I go and get her. Her room is completely baby-proofed so it's the one place I can leave her without worry for a little while (ie like while I'm taking a shower). She has a gate at her door so rather than closing the door on her, she can see out and call out to me to let me know she's awake. If she does wake up at night, it's nice to slide in next to her on the bed until she falls asleep and then I can go back to bed. I thought it was too early to move her but now that she's so happy and she's sleeping through the night again, it's been a wonderful thing. We're planning on having a second child soon so this also frees up her crib for the next baby.