I've been looking around for home warranty, and many of the plans say that pre-existing conditions are not covered. This makes me a little weary because I imagine that once anything breaks it could fall under the pre-existing conditions clause and the warranty wouldn't kick in. So my question is: without an initial inspection (which none of these companies mention) how can you prove that a condition was not pre-existing at the time you signed up for the warranty?
In my experience, they will rely on the evaluation of the service person that comes out to perform the work. In most cases it's pretty obvious that something was a pre-existing condition or now.
If you read the conditions more carefully, it probably says something along the lines of the problem must be apparent to a regular user in the course of normal operation. So a slow water leak that has no symptoms for weeks but actually predates the warranty should be covered.
My sister bought a home that had a home warranty like the ones you mentioned. The previous owner installed the water line for the ice maker incorrectly so when when she turned it on the kitchen was flooded on the first day of owning the home. The warranty company said that this was a "pre-existing condition" because it was done wrong by the previous owner. Her current homeowner's insurance had to pay most of the cost. They will find any reason they can to avoid paying for damages.
In my opinion it depends on the house. If everything is in good shape you should just take the money and put it in the bank for future repairs instead of betting that whatever breaks will be covered. Insurance is just like real gambling, the house always wins.