Hi Christina, I think Paige is right about our perception of there being issues with Savannahs. It does seem that people post a lot about their problems here, but if you realize that there are almost 1000 members on this forum, and many come specifically because they have an issue and are seeking advice, the percentage of issues vs. perfectly happy and healthy Savannahs is pretty low.
As for the litter issue - I have never heard of that before, and am not quite piecing together how a particular litter can cause problems with burning butts, when the butt never touches the litter. I would like to hear more about this, if your breeder is able to give you more details.
As for being a distinct breed, I'm not clear what you are saying there either, the Savannah is a distinct breed recognized by TICA, and the kittens are often priced the same as any purebred kitten, although those foundation cats with higher Serval TWiG (theoretical wild gene) are often priced higher. This breed has been around now for over 25 years and is the fourth most popular breed with TICA, meaning there have been literally tens of thousands of Savannahs registered, and probably many more that have not. In spite of this, we have not yet identified any breed specific health problems, which is I think a good sign, although as you say something can always turn up in the future.
Again, the Savannah is a domestic cat with an exotic heritage, it should be treated just like any other domestic cat, with very few (if any) exceptions, so it really shouldn't matter whether your vet has experience with exotics or not. I think it's more a comfort level for vets if they have never handled a cat that has an exotic ancestry before, but our reassurances that he can handle the cat just like any other (active) domestic can should reassure him/her.