We have Trupanion (Canada) for our Enzo, enrolled him when he was 7 months old - No pre-existing anything. We pay $50. a month, which is one of the more expensive ones in Canada, however, it has coverage for genetic/heriditary illness & no limit. It was a no brainer for us...Even if we saved the $50. a month or $600 a year, if something were to happen that amount saved would not be nearly enough to cover the costs.
True, you have to come up with the money upfront, which you would have to anyway without the insurance, but getting 90% BACK is what helps me sleep at night.
I think it is totally worth it for our little man...its the same reason we have house or car insurance.