Most people would describe the flavor of ethyl salicylate as sweet, wintergreen, spicy and anisic. See http://www.thegoodscentscompany.com/data/rw1001561.html#toorgano
(wait for the advertising page to pass). As such, it appears attractive as a potential ingredient in root beer, replacing some or all of the methyl salicylate. However, be forewarned that, due to genetic variations in olfactory sensors, it tastes very different to some people. I know because, to me, it tastes like walnut and wintergreen with the walnut the stronger of the two. Walnut flavor does not belong in root beer! So, if you are making root beer for nobody but yourself, fine, try it. But, if you are a commercial manufacturer who uses it, don't be surprised when your root beer gets bad reviews!