..."it lets you do a room layout, multiple 3D views, and then you can do a virtual 3D walk-through of your room. You are limited to the furniture provided, but most of it is fairly modern and generic. On top of that, you can change finishes, flooring, wall color/type. When you're done, you can print it out all to scale.
I call it my "virtual dollhouse" and have been having fun trying on different pieces of furniture and for trying different room arrangements. And it's free!"
Sounds like a fun way to lose a lot of time, not unlike The Virtual Model.
And check out Jenny's 3D walkthrough of her apt-to-be.