I was Protestant for 16 years before converting to Orthodoxy. These are some of what I consider to be the fatal flaws of Protestantism.
Included are the Protestant challenges given most Mondays in front of Willard. Feel free to contact me if you are up to the challenge.
Rock and Roll Worship
It is nearly impossible to practice the Christian ideals of asceticism and self-denial while you are having a party.
Protestants have a misguided view of salvation, not to mention that nowhere in Scripture is it written that faith alone saves us.
The problem with sola scriptura is two-fold: It is not biblical nor does it work in real life.
Totality of Scripture
There are certain passages of the Bible that Protestants simply cannot fulfill.