Floating point equality

However, I wonder, are there any cases, when using == is perfectly fine?

Sure there are. One category of examples are usages that involve no computation, e.g. setters that should only execute on changes:

void setRange(float min, float max)
{
    if(min == m_fMin && max == m_fMax)
        return;

    m_fMin = min;
    m_fMax = max;

    // Do something with min and/or max
    emit rangeChanged(min, max);
}

See also Is floating-point == ever OK? and Is floating-point == ever OK?.