I purchased the case for the M6 about 2 days after having the M6 keep slipping off everything. The case, fits tightly like a glove and is very well made.
The M6 is an amazing Android-based player - fast, feature-packed and quality built ... but because of the glass on both sides, it *is* a slippery son-of-a-gun. The leather case - as the player - is quality built and offers both a nice level of protection and a less slippery surface than the player alone. Definitely an accessory you want to buy.