I have had several and bred them. The hairless dogs are very, very sweet. They haven't got a mean bone in their body. I have NEVER seen a hairless one that was completely housebroken. I have heard people claim they were, but in all truth they still have "accidents". They especially like to poop in shoes. The hairless hairless ones loose teeth as they age. My 2yo has already lost 3teeth and has one more loose. The hairy hairless ones seem to do a lot better with their teeth. And of course powderpuffs have no dentition issues. They do bark a lot, and many howl in a woooooo sound, but not all howl. And they are sweet and funny. In all honesty, I prefer a cross rather than a purebred crested, but I have had both. The purebreds go about 10-15lbs. Even the pink (hairless) ones tend to darken up with age, so they look kind of dusty brown. And they lighten in winter, darken in summer.
In purebreds there is a genetic disease that has become a problem in the breed that causes ataxia and death. The AKC has sent out information on it once. It is not common. Kerry Blues also have the same issue.
About the housebreaking, there are some small breeds that are very difficult to housebreak completely so that there are never accidents. Shih tzus, beagles, pekes, etc are notorious for housebreaking issues too. Chinese Cresteds are just like those, so it may have more to do with them being a toy breed rather than being hairless. But from experience and from hearing many people talk, I can tell you that housebreaking is an issue with the hairless ones.
They are not nervous, timid dogs. They are very sweet to everyone canine and human.