the problem with some of those warranties is that the give you warranty on the engine gearbox and diff..
but in there fine print it does not include any gaskets or consumables..
so things like an oil leak, leaking head gasket, worn brake pad are not normally covered.

but if the engine gets a bearing knock,burns or drops a valve or throws a rod they will only cover the first $1000 of repaires..

so read the conditions of there warranty before you aggree..
i have brought cars from car yards but normally offer them cash at a substantially lower price that they are advertising, and tell them to forget the warrantiy as i know that there warranties mean s**t...