The attributes listed in this thread are the experiences of each individual and your experiences may differ with your individual bird.
I can't believe no one has done one yet, so I guess I'll start.
Please add your own experiences, while I have nearly 13 years experience, it's all with the same bird.
Keep in mind every bird is an individual, and as such this will not apply to every lovebird!
My own experience is with a singly-kept, tame, hen, so I will be mainly focusing her. Please keep that in mind.
The Good
Peanut is tame and views me as her mate. She is very sweet and would like nothing better than to spend her entire day near me. She loves scritches, cuddles, and will fall asleep in my left hand while I scritch her. She likes to sit on my shoulder or chest, as close to my neck as she can get, and just huddle there. She loves napping in the recliner with me.
She plays like a velociraptor, running at something, jumping onto it to grab hold with her feet, and bites it repeatedly. She'll flap her wings and make the toy slide everywhere while she "attacks" it. If it's small enough she'll slide it around rapidly with her beak and chase it. She loves to push and throw things off the computer desk and watch them fall to the floor. We play catch, where I'll catch an object and throw it back, and will toss it back and forth until she "wins" and I miss. She's a sore looser though, if it goes on too long she'll carry to the back of the desk and drop it off herself!
She also loves to shred, and it's pretty cute to watch.
Lovebirds, as a whole, are super-adorable. This is fact.
They aren't known for talking but are able to mimic sounds. Peanut has a small repertoire of clicks, trills, kisses, whistles, and er, fart noises (it's actually a raspberry.) She also surprised me a few years when she started repeating a few phrases. However her voice is extremely high pitched and difficult to understand, most of what she "says" I have figured out simply based on the number of syllables in the squealing. A few months ago she's even started mimicking my laughter. It is the lowest pitched noise she makes and it sort of sounds like I may need to hire an exorcist.
I would say, generally, she is about as smart as an average dog. She could even escape from her old cage, I had to put locks on the feeder doors. The few things she does say, she says in context, especially the laughter! She'll laugh when I wouldn't, but she is doing something she thinks is funny (like pushing a glass of water over and making a bid mess. I didn't laugh, I sighed... she did however.) Kiss noises when she's feeling loving, things like that.
(I do not own another bird I can compare her to, but her problem-solving and general intelligence is pretty much equal to my Labrador mix.)
The Bad
Unlike another lovebird I simply cannot spend the entire day with her. Also unlike another lovebird, at night we each go to our own "beds." Like naps, she would love to spend the entire night near me too but that just isn't safe or practical. It's definitely one of the areas where I feel having her bonded to another lovebird would maker her happier.
However she's also extremely bird aggressive. Female lovebirds are known to be territorial and Peanut has taken this to an extreme. Boarding her at the vet's house revealed she doesn't tolerate any other bird, big or small, in her line of sight. She tries to attack them without any other provocation than existing.
She is very determined to nest. Don't leave important paper around your female bird or it will be bitten into strips, tucked into her butt, and carried back to her nest. Uncashed checks make the best nests.
She is also territorial and will defend what she thinks is hers with her beak. Lovebird beaks are sharp and powerful enough to go through skin if they want. She's even cut me on accident with the tip of her beak it's so sharp. Some of the things she will defend with force are actually mine. She's bitten me before for being too near to her latest nest that was the inside of my shirt
I was wearing.
Mostly though she gives clear warnings and I am rarely bitten unless I miss or ignore them. She doesn't want to bite, it is just part of her nature to defend her territory so she will if she feels she has no other option. If I respect her instincts we get along very well, in fact I don't think I've been bitten yet this March.
A few rare objects will elicit an immediate attack though, and they get added to the "banned around Peanut forever" list.
While lovebirds aren't nearly as loud as medium or larger birds but their shrill, piercing contact calls are like nails on a chalkboard to some people. When Peanut wants to be heard, I can hear her anywhere in the house and outside the house with all the windows closed. However she is not loud enough to be heard around 40 feet away from the house.
They will still chew on things they aren't supposed to, like all parrots, but little beaks mean smaller damage.
The Ugly
I'd be inclined to say "there is nothing ugly about lovebirds" due to their status as one of the cutest things on the face of the earth but there is one thing...
Peanut is fearless. She would take on any thing of any size if she thought she needed to. Lovebirds can and do attack other birds of any size, and the results can be ugly indeed.
Smaller or more gentile birds like tiels and budgies have been killed and maimed by lovebirds, and lovebirds have "kamikazed" themselves on much larger parrots, resulting in their own deaths or severe injury. Two lovebirds will even fight and kill each other over territory, females being the most notoriously territorial.
I've even caught Peanut sizing up my dogs from her cage before. My dogs are not small.
(They are never, ever, allowed near the room where Peanut lives while she is out for reasons that are probably obvious.)
I hope this post is adequate, please contribute.
