My copy of Sonic the Hedgehog 2 finally showed up from the U.K. yesterday.
VERY happy with it. It plays so much better on the Master System than it does on the Game Gear. I'll be seeking out the first game and Sonic Chaos on Master System now, too.
However, it does have this ugly light-blue border around the game that I don't like. It would make me think it's a direct port from the Game Gear version, except, like I said, it plays so much better than the Game Gear version.