I tried it, but didn't like the flavor. It was like drinking tree bark. It also gave me heart palpitations, probably due to the high caffeine content. I didn't try it for the weight loss claims, since those appear to be unsubstantiated, but because it sounded like an interesting beverage with a unique cultural history. I like trying new things
SpecialTeas offers some interesting sounding flavored mates at
http://www.specialteas.com/Yerba+Mat.../category.html and they offer sample sizes for a dollar.