I don't carry a torch for Rand Paul, but I am grateful for his act of resistance.
You ask what effect is achieved by his resisting. I will reply, unromantically, almost none.
We could argue about public education (did he really reach anyone new who doesn't already know the Patriot Act is evil?) and about self-aggrandizement (was he merely campaigning?).
To my way of thinking, we are living in a time when our votes count for little, our representatives do little for us, and against this condition of a democratic people isolated from control of the state, a sickening reversal of control is instead true: the security state is ascendant and it is our freedom that is waning.
If my apprehension of our position vis-a-vis the state is correct, this means that most protest will be reduced to a minor symbolic key. Its value, then, is in what it symbolizes, and I would say a filibuster on this point of authoritarian government power symbolizes a refusal to surrender casually. A refusal to be cheapened to the point of not caring; a defiance.
Quantifying such things is easy. What is the net benefit? Again, almost zero. But not entirely. A spark is kindled, or if you prefer, a flicker is kept going in a small and dull flame, with the hope that later we may fan it into something bolder and more valuable.
The value of this filibuster is sustaining hope.