Who does not want to have a pet?
Pet interaction with the sim seems a little off. But its like there interaction with any other object or another sim. Its a Bit off but has that "Sim" feel we all know and love. Training is a bit time consuming but there are schools. I haven't tried any of the job tracks for your pet yet. But they do seem very interesting. The characteristics of a dog seem spot on when left as default. I made a Pit Bull and it started to destroy my house. I had to scold it many times. Also the dog is hyper and loves to play. So having a pet will take time from your sim, like in real life, and require good ole TLC.
This expansion pack does not add things like new lots or a new area. put it doesn't need to either. If it did It would probably feel like fluff and we would be missing something important. The pets behavior is by far better then what i expected. Maxis did a very good job with training a pet and keeping there actions random. The pets seem "life like", well as life like as any sim should. Only having this game a day I have not found many major bugs (i am sure they exists as with any new expansion). This game is well worth the price tag. This expansion is also one of the ones they are a must have.(along with Nightlife).