Words Fail Me - What Everyone Who Writes Should Know About Writing."
If you use the word "it," O'Conner tells us, be certain that your reader will know immediately what it refers to.
I agree. In today's world, where marketing success depends so heavily on being well-indexed in the Internet search engines, there are two reasons to abandon pronouns such as "it," and instead use nouns and noun phrases such as WinWidget, the program, the application, and the software.
First, as O'Conner points out, using nouns is clearer than using pronouns.
Second, using nouns makes your writing more keyword-rich, making it easier for the search engines to rank you for important words and phrases.
Today, we're all writing for our human website visitors as well as for the search engines. So we need to use both nouns and pronouns. Carefully.