Nagarjuna and the Schools I am confused by the variety of views within Buddhism. It appears to me that Nagarjuna provides a complete philosophical justification and explanation for the Buddha's teachings and that this is accepted by many Buddhists. But not all. I'd like to ask:  


Which sects or schools reject Nagarjuna's metaphysics? 
On what grounds do they do so? 
How do they deal with the difficulty that Nagarjuna proves all theories of Reality except his own are logically indefensible?


There are three issues here: there is N's proof of the absurdity of all positive metaphysical positions (in Fundamental Wisdom); his 'theory of Emptiness'; the doctrine of 'Two Truths'.

I wonder whether some Buddhists cherry-pick from these -- or do those who reject or accept one of them tend to reject or accept all three?
I can tell you why the Theravada school does not pay attention to Nagarjuna's works:


Parable of the Poisoned Arrow
Parable of the Simsapa Leaves
The Discourse on the Unconjecturables
The statement by the Buddha that he did not hide anything in a closed fist.
Discourse on The All


Basically, this means that from the perspective of the Theravada school, everything that the Buddha had taught in the Pali Canon is sufficient. Nothing more is needed. Anything else is simply icing on the cake.

Personally, I have tried to understand Nagarjuna's Madhyamaka emptiness and tried to link it back to Theravada emptiness in this question. I appreciate the concept of Madhyamaka emptiness.

I don't think Nagarjuna is in conflict with the Buddha's original teachings (in the Pali suttas and Mahayana Agamas). But at the same, I don't think he introduced something new to improve the Buddha's original teachings.

One important contribution of Nagarjuna is the use of methodical philosophical analysis to defend Buddhism against attacks by Hindu and other non-Buddhist Indian philosophers. See this answer.