Truman Capote's own laugh was considerably deeper than his speaking voice. Hoffman nailed it.

Truman Capote was an eccentric,attention-seeking fame-whore
Likely was, but also a great writer.
Hoffman was a great actor, I wanted to like his performance but just couldnt.
Perhaps, because you found it hard to separate Capote's strengths from his flaws.

I agree with your assessment of Truman Capote.
He was also a brilliant writer. But he was not an appealing person.
Most people are complex; good and bad aspects. And I think Hoffman did a great job portraying this. One needs to separate the character being portrayed with the actor's performance. I also think Miller's direction, "distant, cold, indifferent", was on purpose to frame Truman's character. It worked for me. A dark, sad film.
Agree with this post in general, and what I highlighted in particular. Like you, I think that he was a brilliant writer, but like another poster said in this thread, he was also a fame-whore.

I agree with your assessment of Truman Capote. He was also a brilliant writer. But he was not an appealing person. Most people are complex; good and bad aspects. And I think Hoffman did a great job portraying this. One needs to separate the character being portrayed with the actor's performance. I also think Miller's direction, "distant, cold, indifferent", was on purpose to frame Truman's character. It worked for me. A dark, sad film.

I didn't have a problem with PSH's portrayal really, that said I did find myself not liking the character of Truman Capote. Indeed he was shallow and was a liar, I guess if I had to pick I'd prefer PSH not portray him with as much humanity. Not a total sociopath but Capote, in real life, didn't strike me as terribly likable or trustworthy.
Speaking of good portrayals, Clifton Collins Jr should have gotten the Oscar nom that Keener got.