Well, all the negative things are still worth it, but since you're asking:
-The mess. I'm a neat freak so I don't just vacuum once a day, but MANY times a day. That's probably a bit OCD, but I try to keep the floor clean. Flung food on walls and floor just has to be cleaned, and frequently.
-Greet-the-Day noise when you want to sleep in on a lazy, rainy Saturday morning. Uh, no more of that. Cage covers? No. Mine chewed nice holes in those like the first day and then you just get this eyeball peering out at you.
-Moodiness. Sometimes, they flat just aren't in the same mood you are. Just because it's a good time for you to sit and snuggle, doesn't mean that's good for them. Respect the mood or ask for the bite.
-No more vacations or, heck, even ALL DAY excursions. Not that I'd have a good time anyway, I'd totally be worried about my birds. Who could or would take care of them like I could? When I leave them for a few hours even I feel guilty.
-Expense. Parrots are expensive! Their food is expensive; their health care is WAY expensive; their cages/playgyms/aviary are expensive; their toys are expensive. If you're an animal lover but not super wealthy, you learn to budget for those expenses and give up other things. I recommend a savings account from DAY ONE of owning a parrot for their upcoming health care. When it comes (and it will), you will go through that fund rather quickly. You also learn to get creative with making toys. My Grey's favorite toy is cut up drinking straws and colored construction paper loaded onto his foraging skewer. Every empty box from crackers, pasta, cereal becomes a toy (an almond inside an empty box is a favored toy, too).
-Dander. Forget wearing black or solid dark colors. Choose prints (the poop on the shoulders doesn't show so bad

). Oh, and you'll be dusting a LOT more.
That said, it's all totally worth it. You asked because you wanted to be ready for the good and that bad, and I think that's a very mature way of thinking.
P.S. The worst bite I ever received was from a macaw. I probably deserved it (I was caring for her for a sick friend; she missed her dad and was anxious and confused). She bit me so hard on the forearm it bruised the bone and left a knot that took months to heal. I've had a healthy respect for macaws ever since.