It might just be shitz tzu's. We have one family that boards their three shitz tzu's and they are all former show dogs and they all have attitude. They can be very cute and playful, but you have to proove yourself before they'll let you near.
We don't get many Havanese at the kennel. I've seen a couple and they've been very nice. Louise very much admires the breed.
I think one of the major issue with toy breeds is the idiot factor, but a slightly diffrent idiot factor then other dogs. You have to let them be dogs, and way too many owners treat them like little babies or stuffed animals, but don't do stuff like teach them to walk on leashes or even go outside. We have a lot of toys that don't even go outside to potty. They are trained (usually poorly) to use WeeWee pads.
They should be small, affectionate DOGS, not obnoxious, nasty, hyper, helpless little things.
We get a lot of really stupid, ugly bicions, which is grates on my nerves, because the nice pretty ones arn't really half bad. The good ones are fluffy, sweet armfuls of love and can be quite playful and bright. It's not a breed I'd personally really want, but not bad. You just don't see many due to bad, puppymill breeding and idiot owners. It's really sad.
I would like some toys, particularly affinipinchers, lowchens and pappions, as well as poms at some point, but it's definatly going to involve a serious study of avalible breeders before I'd touch one.