I failed my test using a different provider, then used TTP and passed easily.
After failing my exam the first time using a different test prep provider, I turned to Teachers Test Prep to see if their material would prepare me better. They definitely had more helpful material. The organization and structure of the website was particularly helpful, especially with specific lessons to as "why this matters, and you will likely see this on your test." There wasn't a lot of unecessary fluff, just to the point and helpful. I would highly recommend Teachers Test Prep to anyone attempting to pass a California Credential for Teaching.