Westley can say something other than "as you wish"
Westley dies
Westley returns, he is on a ship following Buttercup's assailants/capturers
Westely comes off ship as a pirate, chasing after Buttercups assailants/capturers
Westley speaks for first time (that we know of) since he "died".
Reveals a bit of character. (Seems to be) polite
Encounters first obstacle, one of Buttercup's assailants/capturers. We see that he is polite and can hold his temper as he can hold a polite conversation with his dueler and is not so quick to make assumptions about him.
Westley encounters second obstacle. We find out he is agile and quick witted/intelligent. He beats someone twice his size and more than twice as strong in a "fistfight" using wits instead of strength.
Westley encounters third and final obstacle. The head assailant/capturer. He beats him with intelligence. We find out that Westley is smart but does not over-think
We find out he does kill, but only when deserving. (Though, I disagree with the killing of the boar thing unless it was going to die from it's wounds anyways.)
Westley is good with words. He can hold a conversation with his "true love" and not reveal to her who he is.
Becomes more personal and obvious with words when alone with Buttercup in "fire swamp" (or what it was called, I forgot the name)
Westley was acting on own behalf. Had own intentions and plan.
Captured and went through "the machine",
Died again
Revived again
Stops being mysterious and goes straight to the point. Shows this when trying to make plan with Fezzik and Inigo.
Exercises intelligence by making plan to save Buttercup
Westley disappears from Fezzico and Inigo without warning. Lets us know he still has characteristic of own intentions and acting on his own behalf.
Distracts King while friends/backup comes. Shows Westley's ability to think ahead
Still has mysterious quality. He stops Buttercup in a way which was (probably) dangerous but more effective.
Idea of killing changed since he did not kill the king. Either that, or he considered the people. (If he killed the king, the kingdom could be thrown into chaos.) I cannot tell. (I am aware there may be more answers)
Rides off with Buttercup and lives happily ever after. The End!