Is Gu Yangfeng's calligraphy worth collecting?

Worth it.

Teacher Gu's calligraphy absorbed the essence of the ancients, and applied the rhythmic dance of music, poetry, calligraphy and painting to it, and his calligraphy attainments reached a superb and self-contained realm.

Wen, a famous master of Chinese studies, gave him three golden words because of his name: the beautiful mountain is called the valley, the English and Chinese are called the young, and the neutral one is called the rich.