dianeb1944,
As far as taste goes, agave nectr should not make a whole lot of difference. However, if you are concerned about blood sugar, you might want to look at some of what Jeff Novick has said about it, including in this forum. Agave may not be what we hope for when we see its low glycemic index.
Following is a link to an article entitled "Agave: Health Food, Health Fad or Health Fraud?" written by Jeff N where he concludes "... limit your consumption of all refined and/or concentrated sweeteners and if heart disease, elevated triglycerides, insulin resistance, diabetes and/or weight are concerns of yours, avoid the ones higher in fructose, especially agave."
http://jacknorrisrd.com/?page_id=904A single serving of the salad dressing probably includes only a small quantity of maple syrup/agave, but I would imagine a lot depends on how much sweetener you are eating overall.