What can we say about it? See what they (hearing people) say about it. The most common terms described include: "beautiful", "expressive", "fascinating", etc. Those descriptions are on the surface of seeing sign language.
A little more descriptions are coming from those hearing people who are signing.
"[Sign language] is, in the hands of its masters, a most beautiful and expressive language, for which, in their intercourse with each other and as a means of easily and quickly reaching the minds of the deaf, neither nature nor art has given them a satisfactory substitute.
"It is impossible for those who do not understand it to comprehend its possibilities with the deaf, its powerful influence on the moral and social happiness of those deprived of hearing, and its wonderful power of carrying thought to intellects which would otherwise be in perpetual darkness. Nor can they appreciate the hold it has upon the deaf. So long as there are two deaf people upon the face of the earth and they get together, so long will signs be in use." -- J. Schuyler Long, Head teacher, Iowa School for the Deaf. The Sign Language (1910)"
"Sign language is the equal of speech, lending itself equally to the rigorous and the poetic, it philosophical analysis or to making love." -- neurologist Oliver Sacks (1933-2015); author of Seeing Voices: A Journey Into the World of the Deaf (1989) and many other books.
More to come...
But, wait till you see talented literary arts in poetry, storytelling, and calligraphy (only if you know advanced ASL enough) and further understand the literary elements. You'd be blown away. :)
Related posts: What is and what is not sign language.