It wouldn't count as a fruit, it's still an added sweetener like sugar or honey. It doesn't have the vitamins, antioxidants, and fiber that fruits provide.
It is preferable by many because it has a low glycemic index. It's also sweeter than sugar, so you can use a smaller amount for the same impact, but with fewer calories. It's used by a lot of South Beachers, as well as dieters that follow other diets.
I prefer it because it's environmentally friendly, unlike sugar production which is a major cause of erosion of the planet. Agave nectar comes from the fruit of the agave plant, which is easily grown organically. The large fruit is tapped twice a day for nectar, which it quickly replenishes. One plant can make up to 2500 liters of nectar per year, and each plant can live for many years, making them powerhouses of sweetener, with very little impact on the earth - or our bodies.
That's the story on agave
