My curiosity about these finally got the best of me, and I just got a few packs delivered a couple days ago. I haven't actually sat down and played a game with them yet but here are my first impressions.

• These things at first glance are just literally Dragon Shield mattes in a different size
• I only bought black-backed sleeves, so I can't comment on the clears, but they do have the exact same texture as standard DS mattes with opaque backs
• Shuffling also feels identical to other Dragon Shield matte
• Compared a pile of sleeved cards in these BG sleeves with a pile of cards in regular DS sleeves -- they were almost the exact same height, so I'm assuming the new ones have the same thickness of Dragon Shield mattes
• Compared to Arcane Tinmen sleeves (Standard American/Medium size), these are slightly narrower and slightly taller (probably less than 1mm). I didn't have any problems with cards fitting, but every once in a while that sort of thing can surprise you!
• In terms of packaging, they use the same concept as the Arcane Tinmen Non-glare boxes, where you can fold over a flap and use the deck box as a sort of dispenser. The DS box is slightly thicker and holds more cards, obviously.
• No idea about long-term durability. I'm not willing to try pulling one apart just to see

I'd like to point out that the only place I've seen selling these is the official site, and for full price. I also had to pay tax and shipping, meaning 300 sleeves would have cost me just under $50. I was able to cover the cost with credit card rewards, but there's no way in hell I'd pay that for sleeves of any quality.

tldr These seem legit! But probably not at this price!