I've been using this bed for a few years, and finally writing a review because I am so happy with it.  Doesn't wobble - very sturdy.  My mattress doesn't fill up the space allowed, so it should fit any brand.  I have an extra 3" and can see the slat boards. Not sure what brand my mattress is, but it was expensive and organic and it quite deep so I feel like it wouldn't be one of the smaller mattresses.  I would buy this bed frame again.  It has held up well.