I disagree. There are so many different insurance companies, there ARE some that will cover reoccurring or preexisting conditions. That's why you need to shop around and see whose coverage best fits you and your pet's needs.From my understanding, you still must be able to pay the vet bill upfront - you get a reimbursement later - so in that regard, if you need the money immediately and you're considering it for the reason of being tight on cash, it's still useless.
I see it as a waste in most situations. From what I've seen, they do not cover if the problem is reoccurring or preexisting, making it fairly useless for a lot of serious problems.
I think it would be a better idea to save up money yourself. Set that money aside for emergencies in your own savings account.