Hi. I have 3 that I have transitioned out of cribs. With all of them, we didn't even bother with a toddler bed because the time they can actually use it is so short that it seems impractical to even buy one. Around 18 months, we just took a twin bed off the frame and put the mattress directly on the floor (without the box spring). It took a little getting used to not being "trapped" by the bars of the crib, but within a couple of months, all three had gotten used to their new beds and enjoy sleeping in them. Sometimes (especially at naptime) we would find them on the floor somewhere instead of in the bed, and we would put them back in for the remainder of the nap, but they almost always end up back in bed for their night's sleep even if they don't stay in bed from the beginning. I don't recommend putting every child into another bed at 18 months. We only did so because we were going to need the crib again. My oldest is 3 1/2, next are 18 month old twin boys (who have been sleeping in twins on the floor since 15 months) and a 4 month old girl. We kind of recycle through cribs pretty quickly. But they have all loved the "new" bed pretty much right off. I think they like the freedom of not being stuck. They also like the bigger twin mattress as opposed to the small crib mattress. At 27 months, maybe your son just wants some more space...