I have delt with alot of people on tradgang, and (knock on wood) have never had a bad deal.
And this is everything from buying/trading bows, arrows, dvds, you name it. I would say that 99 percent of the people on here are above average folks with high morals and values, the kind that give you their word, and it actually means something.
Unfortunately, I believe that six months is way too long for a deal that should have taken no more than a week or two at most.
To make things right... He either needs to return the knife, or produce the arrows he originally was supposed to make for you.