Hi Iano,
Although salvation by faith in JC removes the arbitrary good-works cut-off, what about the continuum of doctrinal difference? How doctrinally sound do we have to be to ensure our faith is in the correct JC?
I know many who consider the theology of Benny Hinn to be sufficeintly off-base to place him outside of sound and hence safe doctrine (see e.g. Christianity in Crisis).
What about super-exclusive Christian groups: Bretheren, Jesus Army, etc.
7th Day Adventists? Christadelphians? What about Jehovah's Witnesses? Mormons? etc, etc...