Like CandyDane, I prefer a bare reader at home. The lighted case is convenient for those times when carrying a separate light would be inconvenient, but it's chunky and the battery life doesn't hold up to the long reading sessions I indulge in at home.
Of the dozens of reading lights in my drawer, the Belkin is my favorite. It works with or without a case and it casts even light over everything from my PRS-350 to my Kindle DX. Three AAA batteries are the heaviest component, but the actual light weighs almost nothing. I've used it daily, for almost six months, as a reading light and as a flashlight. Battery life is great.
http://www.amazon.com/Belkin-Clip-Re...dp/B003HKRVAW/
Based on reviews, I'm in the minority with my intense dislike of the Kandle. I found the illumination annoyingly uneven and its limited adjustability means that it casts a shadow on the recessed Sony screen. If you position the light too far back, the clip causes the shadow, too far forward, and the the shadow is cast by the reader's ... bezel is the wrong word, but I don't know the right one. I have two Kandles, and I tried using them in tandem to enhance the light coverage, but the result was unsatisfying.