I've had my sun conure for 13 years so far and in my experience:
Good: Loyal, likes to spend time with me while I do other things and loves to sit on one of the kitchen chairs while I eat. He more often than not warns before he bites (by opening his beak at you), unlike my late but very loved Quaker. While his decibel level is loud, he doesn't often make his full squawk/scream unless calling for me or if he sees a vaccum cleaner (he hates those).
Usually just makes little soft squawks that aren't even noticeable if you're not in the room with him. Seems to enjoy car rides. Great flyer, can fly up and down stairs on his own without getting hurt. He's one of the most intelligent pets i've had as well. Not an escape artist type. When he wants to interact with you, he's very gentle. While very limited, he can say a couple words (and mimic coughs lol) Healthy and sturdy.
Bad: Not cuddly, I see most sun conures described as cuddly but he is definitely not ,hes a sit with you kinda bird more than he is a bird for touching. I can pet him when hes in the mood (and always when hes coming back from the vet, I think he needs comforting). Only I can pet him though, no one else. Very jumpy as he's grown up. He doesn't freak out easily but he gets startled by any sudden noise like ripping paper, closing a cabinet less than softly,etc. He can't handle being away from me for long periods without being seriously unhappy, making trips difficult. Picky with food- won't convert to all pellet diet, won't eat natural type pellets. Throws what he doesnt want out of his bowl. He is pretty messy- throws stuff out of his cage quite often even when its not food.
Ugly: Cage aggressive and territorial. Dive bombs people who enter my room if he's out on top of his cage unless its me. Fights with towels and blankets. You can't perch him directly in his cage or he will bite you, you have to offer him his food bowl or something else to sit on- OR wait for him to fly to you of his own accord. He seems to be one of those birds that doesn't like people the opposite gender of his owner for some reason. He doesn't like other animals, bird or not. He either tolerates them or dive bombs them. Sometimes very random objects make him get upset. For example, one time I crinkled a water bottle and he bit my ear!
Overall though,despite his weird little triggers of all the pets that i've had (multiple budgies, a cockatiel, 2 dogs, a rat,a guniea pig, a rabbit and a quaker parrot) he is one of the simplest to care for. He really just wants to spend time with you and have a little treat every now and then and he's happy.