J.S.
I have had traditional wood bunks and the tubular futon loft bunks. Both are easy to assemble you just have to follow the instructions.
I would say avoid the cheap stuff until you know what you are doing because their instructions blow and the quality is awful. That equals a furniture life span of about two years.
I feel I must explain, when I say cheap I mean 100 dollars for the bed. I am not saying go out and spend thousands.