Well, you asked for opinions...
I didn't have much luck the one time I bought one and tried to use it. However, this is an area where the company you use and the particular contract can make a difference.
Get a copy of the contract, before you sign, and take it home to read, carefully. Highlight any areas where you have questions and don't be afraid to ask the questions. If there are too many possibilities in there that they will not cover items, and you don't get satisfactory answers to your questions, then it may be the wrong one for you.
Mike: 1997 SE w/ 183K, aka White Horse
, Gutted Airbox w/K&N, drilled 180* t-stat, tint all around, clear corners w/SilverStars, "PONTIAC" light up tail, PEMs, NGK TR55s