This Daybed has been great!  Pretty easy to put together (easiest with 2 people), and very sturdy!  We bought two standard twin mattresses and they look awesome!  Wouldn't recommend a mattress any thicker than 10" on the trundle, and the 10" is great on the upper part (you could probably do up to a 13" mattress at the top and it would still look good).  

My sister and her daughter stayed with us and the only complaint for the trundle was that as they were sleeping if the went to turn over to sleep on their other side, the trundle would shift ...  **NOTE** the daybed sits on engineered hardwood flooring, so if you have carpet or a rug this should NOT be a problem!