Very sturdy.  Complicated assembly.  It looks good, is well designed and the specifications indicate it will support a decent amount of weight, so sleepovers will not strain the bed!  We wanted a left side staircase and true to the comments, it can be assembled on either side.  On the downside, the only reason why 4 stars and not 5, the bottom of the top bunk is not finished, so when laying in the bottom bunk you see the wood (unfinished) slats and the base of the top mattress. The screw heads do not come with caps, so they are exposed.  Everything else is nicely designed!