I have my two covered, I have never had to claim but would hate to be in a position where I couldn't pay for treatment.
My sister has four buns all insured and it has definatly been worth it for her, one of her buns has had his incisors removed, they started to regrow and her insureance paid for the removal, another of her buns just had a long bout of stasis, she had to go and see a specialist,the bun stayed at the specialist three nights, plus two weeks worth of medicine, all covered by the insurance, she wouldn't have been able to afford it otherwise! We are both with pet plan, they will cover them no matter how old they get as long as we keep paying, they will also cover any further tooth problems, she had to phone up and negotiate for the toothless buns but her poilcy states he is covered.
I think if you have more than four buns however you are probably best off just saving the money.