So far, so good! The bed arrived early in the morning, so there was plenty of time for it to de-compact (Which is a lot of fun to watch and hear--it snaps the huge bubble wrap while unfurling!). It had doubled in size after 4 hours. After another 10 hours, it was higher than my old bed, and I couldn't resist sliding in. VERY comfortable bed, without a "breaking in" period.
[TIP FOR CARRYING UPSTAIRS: We slid it out of the box, which is awkward and slippery, and it took two minutes to glide it up two flights of stairs, using excess plastic on both ends as handles.]