I bought a "Go" and didn't like it - it's relatively thin, the Kindle comes right up to the edge on the right hand side, offering no protection for the corners of the Kindle if it's dropped, and there's no way to keep the cover closed.
I like the M-Edge Platform for it's padded protection, but it's not the 'perfect' case for me. I've ordered a Noreve, hoping it'll come close enough to 'perfect' that I can stop searching. I bought a used Oberon, which is a gorgeous cover just for the artwork and is pretty good protection, but there's a big piece of wool felt inside that fits against the screen, and since I fold it back and read that way my hand rests on the wool, and I find it scratchy and irritating, and therefore distracting.
There are other threads about covers either on this page or the next one.