A little late to the party, but you can sort of explore in first person by hitting TAB to enter movie making/screenshot mode. In this camera mode, the camera can be moved with WASD, use Q/E to lower and raise the camera. You can rotate the camera with the mouse and use the scroll wheel to change the field of view.
For best effect, you should be viewing the top floor of your house with all walls enabled (you should be able to see your roof with no cutaway) before hitting tab. This way you'll be able to see all your walls and ceilings.
It's not a first person view as such, but it's a good way to do a virtual walk through of a lot all the same.