What is the main debate in the interpretation of "The Road Not Taken?"

In "The Road Not Taken" by Robert Frost, the usual debate centers around the speaker's choice to take the road less traveled. While some think it is best to take the road less traveled "because it was grassy and wanted wear," the speaker tells the story "with a sigh somewhere ages and ages hence." The sigh is confusing because it could be a contented sigh, or it could be a sigh of disappointment and regret. 

The speaker offers no clues about the nature of the sigh, so it is ambiguous and open to debate. The name of the piece itself is interesting and may contribute to the argument - it is called "The Road Not Taken," and not "The Road Less Traveled." Robert Frost names the piece after the road he chose not to go down, which makes the speaker seem wistful for a second chance at choosing between roads. Because the poem is open to interpretation, it is relatable to all who are making similar choices, for everyone learns that choosing a specific path will make "all the difference."

Another topic sometimes debated is the question of whether the speaker has actually taken the road less traveled. The speaker seems to acknowledge at one point that "both that morning equally lay / In leaves no step had trodden black." Does the speaker take the road less traveled—or just the one that initially seemed that way?