My personal feeling about any refined sugar is... avoid it!
We have no need for such sugars in our diet, they have crept in there to feed sweet tooth addiction, reduce the cost of processed foods and to help increase the shelf life of packaged foods.
Agave was hailed as the "greatest natural healthy sweetener" for a while. It got a lot of attention because it is low-glycemic, which is a big buzz word in the health marketing world and is helpful for those with diabetes.
It is low-glycemic because it has almost no glucose, it is essentially ALL fructose. Agave syrup is made from the sap of the Agave plant. In its natural state it isn't very sweet as it's composed of complex fructose polymers called fructosans. The sap is heated for about 3 days to hydrolyze the polymers to break them down info fructose that is very sweet to the taste.
The reason it's low-glycemic is the reason it's not so good for you. Fructose is broken down in the liver and the body isn't used to such a high concentration of processed fructose, ~90%. Nowhere in nature does fructose ratio come close to 90%. Even most HFCS (high fructose corn syrup) is 55% fructose, which is still beyond any natural occurrence of fructose.
Also, don't be fooled by the label "Raw" typically associated with Agave syrup. It is generally heated to temperatures up to 140°F during those 3 days. There is no regulation for the use of the word 'Raw' in labeling.
So there ya have it