Unfortunately for me, I didn't pay any notice to the fact that he used the word "is". And if I had, I would've disregarded it as some cool slang anyway. So, I started thanking him for the compliment, acting (read: faking) humble and surprised and so on. That's when he explained what he had really said:
You is really good.
He had been talking about the Asian guy named Hye all along... That's what happens when you go fishing for compliments. :-)
Hye is really good...