I have a Shih tzu. She is nearly 2 years old... I've had her since she was 8 weeks old from the breeder (I will get flamed for admitting this!)
Pros: I didn't have any difficulty toilet training her, she doesn't seem as stubborn as the others would have you believe, maybe that's just her!
She is the loveliest thing I have ever clapped eyes on.
Cons: the fluff!!! She goes to the proper groomer every month, and she needs a good brush every day, the matting is horrendous if left to its own devices. Hence we need someone we can rely on, and they sort her out.
More pros:
Her recall is relatively goood, although I am hesitant to let her off in the park as I am scared other dogs will see her as a snack.
Her current best friends are border collies, and she will run quite happily with them, she has so much energy (luckily I have the best dog walker in the world - if you are in north London, then I will happily provide his details if you PM me).
Cons: obvious physical risks with this breed. Mine is insured up to the hilt, and has so far shown absolutely no signs of discomfort or anything, perhaps I am just lucky. But with this breed obviously you have to be very careful, because they are brachycephalic, so obviously they need extra care and insurance is higher (obviously).
Basically they are really fun little dogs, but obviously they are dogs, not teddy bears, and therefore must be treated as such. Just because they look cute doesn't mean they don't need any less excercise, Mine needs a good run everyday, at least two hours, And at least one with her collie friends, where she will try to outrun them.
So at the end of this long long post, basically I would recommend a shih tzu, but only if you are actually going to take him/her seriously as another pp suggested. They are not toys. They are (in my case) very active dogs, I would put in the same provision as a lab or something. Good luck!