I put this together by myself in about 3 hours. There are two separate sets of instructions, so make sure you use the twin over full as there are a few different steps between the two. It was delivered by fedex in two separate shipments, so I had the twin over twin before I had the expander to the full on the bottom. 

I agree that there is not a lot of room on the bottom- it would be difficult for an adult to sleep down there- but it is fine for my 4 year old. 

So far so good- I am happy overall