We have the IKEA Kura bed, and use it as a bunk bed. It's perfect for us!! I was a bit concerned about Littleman's readiness for a top bunk bed, since he was only 4 1/2- but he has done great. We bought the canopy that goes with the bed. We have a normal twin mattress on top (my old bed) and an IKEA foam mattress on the bottom. Mr. Sweetcheeks transitioned from his crib to the bottom mattress. I keep a sheet hung over the bottom portion to make a "fort" for him, and he LOVES it. They've both been very happy.
I like that it is lower than a standard bunk bed, wood, inexpensive yet fun, and we'll have the freedom to convert it to a canopied single bed should we wish to later on.
My only problem is that I suspect Littleman being on the top bunk might be contributing to the fact that he is still having to wear diapers at night. After all, it's hard enough for him to learn to wake to go to the bathroom, let alone having to negotiate a ladder to get there! I don't know, because it was a problem even before, when he slept on a mattress and box spring placed on the floor. We don't have space for two beds in there though, so the bunk bed arrangement will just have to do for now. All in all, it has been the perfect arrangement.
Littleman 10/03, Mr. Sweetcheeks 08/05, Babyman 11/07