What kind of man did Draco Malfoy become?
I don't think there were enough clues in the books to answer this, but I also know that there have been hundreds of times when J. K. Rowling has given talks and interviews and talked about her characters, so maybe she's said something about this.
Even though the Malfoys have behaved contemptibly at times, they do draw the line. Draco couldn't kill Dumbledore and they walk away from the Death Eaters toward the end, even though it might not have been safe to do that in the long run.
Is there anything that tells us what kind of man Draco Malfoy grew into? I think the last scene makes it clear he and Harry are at least able to acknowledge each other without hatred, and might even keep in touch, but that's all we see.
Has anything else been revealed about what he's like as an adult?
JKR has said that Draco was "sobered" by his experience as a Death Eater, and that he does not owe Harry a life debt. Draco marries Astoria Greengrass, the younger sister of Daphne Greengrass, Draco's classmate. They have one son named Scorpius Hyperion Malfoy, who JKR has said has a lot to overcome, not the least of which is his name (she meant Malfoy; I thought Scorpius was worse than Malfoy ;). Draco is never a "nice man." He does acknowledge Harry in the Epilogue with a curt nod; JKR says that under no circumstances could Draco and Harry be friends. Here's a funny quote about Draco:
Q: Does Malfoy owe Harry a debt?
JKR: That's a great question and a lot of people wanted to know that. When Dumbledore said to Harry, Voldemort won't want a close associate who is in your debt, I wasn't implying by that there was any kind of magical bond there. It was more that Dumbldore's extensive wisdom and knowledge of human nature, he knew as Harry later thinks in book seven, he knew that Pettigrew would react a certain way to having saved his life. ... He's weak, fundamentally weak. Pettigrew is a very weak character. He's not someone I like at all. He's a weak person and he likes to gravitate to people who are stronger. Dumbledore is right. Pettigrew had an impulsive mercy... would Malfoy be in Harry's debt? I think the very worst burden Harry could have put Malfoy under was this one, that Malfoy has to feel any kind of gratitude. So I tried to show that slightly in the epilogue when they look slightly at each other and there's a, "Hi. It's so embarrassing, you saved my life. No one will ever let me forget it." I think, does he owe him a debt, probably not. I think Malfoy would go back to being an improved version of what he was but we shouldn't expect him to be a really great guy any time soon.
Yeah, I don't see Draco becoming a humble boy-scout after the events of the Battle of Hogwarts. People can change, but let's not stretch it too far in Draco Malfoy's case. I'd say he mostly ended up somewhat like a slightly improved version of his father Lucius, with the added bonus of a little respect for Harry.