I've met quite a few (well, considering how rare the breed is), and at one point did some serious looking-into them.
Every one I've met has had some pretty serious health issues. Seizures, allergies, joint problems. One I used to know was euthanized at 5 for seizures and arthritis. Probably none of this was helped by the fact that only one I know is a decent weight; the rest are very heavy.
The temperment wasn't quite what I had hoped; they remind me a bit like retrievers in the house, always very close and frequently panting
. I had hoped they would be more athletic as a working breed, but the ones I've known would have never handled the moderate hiking I do. Again, some probably because of their weight, but even so, they are pretty ponderous.
We have one very bad Bernese breeder near us who also breeds some Swissies, so half the ones I've met are poorly bred, I'm sure. I've also known two Swiss imports and two from other breeders. In general, they just weren't what I had hoped from my research.