The program is obviously feature-rich in that many functions which more common (consumer-grade) eBook readers do not offer are easily accessible and usable.
What do you dislike?
The program seems more oriented to eBook authors and specialty users (i.e. readers with complex configurations who prefer to "roll their own" eBooks)...
Recommendations to others considering the product
One would assume there is little, if anything, to be lost in trying the product; if one is seeking fully-featured eBook software then Calibre is a great choice.
What business problems are you solving with the product? What benefits have you realized?
In collaborating with an eBook author having access to Calibre assured that any issue encountered with respect to transient eBook formats & providers was obviated by way of a powerful piece of software which provided a "last-resort" capacity in the event of an oversight or other failure of process during a time-constrained opportunity with little to no margin for error.
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