Voyant is extremely user-friendly and the visualizations users create are easily exportable. One can use Voyant without creating a login or downloading anything. Considering its affordances for particular types of work, limitations, however few, should be acknowledged. The most striking limitation is that texts must be uploaded to Voyant. Therefore the text must be in a digital format in which words are 'recognized.' And, the more you try to do with the tool, the messier input, visualization and analysis becomes.
The visualizations one can make with Voyant are great for starting conversations, they can facilitate analysis and observation, and can be used to clearly communicate complex relationships between texts or words. I would recommend this tool most highly for any preliminary scholarly investigation, as well as for pedagogical purposes focusing on interpreting, understanding and producing literary work.
To use Voyant, navigate to its website and past in links, pdfs or other types of text directly into the tool. One can find a number of examples vetted by Voyant's developers in Voyant's documentation gallery. One I found particularly exemplary of the advantages and optimal use of Voyant for starting conversations about themes, word usage, topics and relations between these in texts is Mark Sample's, no life, 1,000,000,000,000,000 stanzas of House of Leaves of Grass.