Ali Hasan Al-Areedh dedicates a full chapter, Chapter 8, in his book فتح المنان في نسخ القرآن to Abu-Muslim Al-Asfahaani. He writes this about him (translation and emphasis mine),
"So who is this scholar who dared
to contradict all Muslim scholars without fear
His life was full of knowledge and work, judicial and political. He was an honorable scholar, literary author, eloquent poet, uniquely genius, great debater, deeply knowledgeable
of exegesis and other disciplines, knew grammar. His peers admitted his intelligence and acumen, quickness and soundness of mind, strength of argument
, thoughtfulness and brilliance.
Historians mentioned that Abu-Muslim was a practical scholar, pious and God-fearing, none have ever questioned his commitment to religion, or alleged aberration in his faith. His mentality was mature
and multi-faceted. He managed to combine the world and the religion, scholastics, legislation and politics. He was so talented that he translated Farsi poems to proper Arabic poems!
He was so good that some Shia claimed he was Shii. Some Hanafi scholars wondered how such a prominent scholar couldn't agree about abrogation. Ibn Hamza Al-Fanaari, in his book فصول البدائع في أصول الشرائع tried to make the case that Al-Asfahaani did not actually deny abrogation, by saying that the difference is only semantics, or that we did not get all that he wrote."