We've had the bunk beds for about a week, but just got the chance to put it together last night.  It is terrific!  It is such great quality and the concept of a full over full is ingenious!  Our 5 y/o son was so ecstatic after it was put together.  It does take quite a bit of time (just under 4 hours) to assemble, but the finished product is well worth it.  The Cool Gel Memory Foam 8" mattress that we purchased from Wayfair is a perfect fit for both the top and bottom bunks.