I have both keets and lovies and I would never leave them unsupervised. Lovies love to bite their feet and tend to be bullies (like Mary mentioned above) Most of the times they leave one another alone but then the other times i have to break up a squabble with a squirt of water! My keets have even been bitten on their feets b/c they were just hanging on the lovies cage. :(
Some lovies can be loud but then it depends on the birds temperment. They always pick the times that I am on the phone to make a lot of noise--4 lovies and 2 keets! LOL!
This is an old pic of the three birds together (9/08)...since then i've added two more lovies.