The most noticeable change is the substitution of “ for ", which doesn't require this package--this package just does it for you instead of you actually changing the character in the HTML text. (The more interesting parts of the package are some alignment and spacing stuff that is less noticeable.)

If you work with monospace terminal/code/markup a lot, you are probably very used to seeing " . But it is definitely well established that “ is appropriate for human text, Word has automatically corrected this for many years.