From Slate:
In the long revolt against inherited forms that has by now become the narrative of 20th-century poetry in English, no poet was more flamboyant or more recognizable in his iconoclasm than Cummings. By erasing the sacred left margin, breaking down words into syllables and letters, employing eccentric punctuation, and indulging in all kinds of print-based shenanigans, Cummings brought into question some of our basic assumptions about poetry, grammar, sign, and language itself, and he also succeeded in giving many a typesetter a headache. Like Pound, who never wrote an obedient line, Cummings reveled in breaking the rules of grammar, punctuation, orthography, and lineation. Measured by sheer boldness of experiment, no American poet compares to him, for he slipped Houdini-like out of the locked box of the stanza, then leaped from the platform of the poetic line into an unheard-of way of writing poetry.
More here.