I think given one will have one's kitty for hopefully MANY years, it is worth spending some time getting to know the breeder and making sure they are someone you wish to deal with . I do think you can know a lot about a kitten's personality at 8 weeks of age, if the breeder spends a decent amount of time with her kittens. Look for comments that are more specific that "very loving, friendly"... listen for specific stories about the kitten to know that the breeder might actually have observed that kitten.
I advise people to ask lots of questions and feel like the breeder has given time and thought to the answers. If they don't have time for that now, they definitely are unlikely to have time for you once they have your money! Most breeders nowadays have the ability to email pictures and little videos... so being able to visit in person is not as essential. It's not always possible to do so, some live in rather remote locations.
I don't think we want this forum to allow trashing of breeders, but by posting here if anyone has anything negative to contribute they can contact you privately I am sure. Be sure to take all comments with a grain of salt. Doing rescue, I've seen some situations where the breeder was trashed but when we got the kitty many of the claims were obviously not true. Good luck with your research!