I've got it. Like a few other people have already mentioned, MS1, 2, and X play like the originals, but MS3 has some slowdown.
All four games play on Level 4 of the MVS. You can't change levels. Credits are unlimited.
All of the options, instructions etc in-between games are in Korean. The actual games themselves play in English if memory serves me correctly.
The packaging is beautiful. A standard jewel-case surrounded by a fold out paper sleeve. Again, everything is in Korean though.
It's not a port, it's the actual legal ROM, so aside from the slowdown and lack of in-game options, it's the real thing.
It was published by Mega, who also worked on MS4.
I ordered mine from Play-Asia as well. They're fast and reliable.