I just picked up an official Sony cover with the built-in light. Maybe it'll grow on me, but I'm not really a fan of it so far. The vinyl and plastic exterior materials, and the looseness of the front cover when closed, make the overall design feel a little cheap. This is my first cover with built-in light, and the implementation of it is pretty neat. I do appreciate that the front cover easily bends back behind the device for convenient one-handed reading, and having a cover on the reader feels like it'll make it easier for me to hold.
I suppose it'll do until something better comes along, but $50 seems a little much for it.