I had one I used for years, made out of an old drawer, with glass on the top, and a bathroom light inside. I found it got hot and drilled holes in the side of the drawer to help let that out, but in the end I gave in and bought a commercial one.
My new one has a slope, is comfortable to use on my lap all evening if needs be, and has a cool, daylight bulb in it.
Of course, I don't use it every day, but when I do, it beats standing at a window, waiting for a sunny day (in short supply sometimes in Ireland).
I am going to make an Affairs of the Heart quilt this year, in tandem with several other members after they finish their Dear Jane quilts - there will be a BOM thread on here for any others that want to join in. The original has a black background (though you could choose something different) and I just discovered that my light box will work with the black to make easy tracing.