LO is 21-months now and we're thinking about transitioning her to a twin-sized mattress on the floor. I heard a lot of people made the transition smoothly, but I also heard to keep them in their crib for as long as possible! She's a cautious baby and has never even tried to leap out of her crib - she's pretty content in there, but if the transition is going to be smooth I'd rather do it sooner than later since Baby #2 is coming in February.

What was your experience like with the crib to toddler-bed or twin-sized bed transition?