I agree about the pets add on! It's a lot of fun, but the animals in need are so hard to ignore, and then pets take over the game.
I have 6 pets in five households, and 5 of them were strays. I always want to befriend and adopt, but I know when I do, my sim's life is pretty much over. My current archeologist sim adopted a dog called Cutie, an aggressive, energetic, stubborn dog, small breed (they poop three times a day) and now the dog owns him. I had him take a vacation to Granite Falls, and all he did was walk the dog and try to keep it from biting passing sims. I finally had a friend agree to keep the dog for a while (that's what I'm trying to rp it as, but I had to transfer between households), so he could devote some time to grinding treasure. Of course, as soon he goes back to the jungle, he meets another sad, hungry, smelly pupper, so... now he has two dogs.
In another family, I tried to take the family cat along on vacation to Mt K, and the cat got so sad. I first I thought it would be fine, the cat slept a lot, which was surprising, because on the home lot it needed a lot of attention. Then one day my sims came back from skiing, and the poor cat's litter box was full, its food had gone bad, and it had thrown up, and it could not be cheered up, no matter what my sims did (a couple of days might have passed, I had aging off, and my sims all had aspiration reward traits that reduce needs). I had a look at the cat close up, and its eyes were teary. I didn't want to end the vacation early, but I couldn't stand it. So I decided the sim who was enjoying himself the least should stay home with the cat, and the other three would go back to Mt. K.
Then, one of my vacationing sims had to run home quickly for something, and the cat ran at them meowing like it thought my sim had died. It was sick, so my sim had to take a break from the vacation to take the cat to the vet. This happened twice.
Other than the strays, though, I love the add on. I even love the way I end up not using my play time as planned.