The TorHans company is bringing some thoughtful engineering into the world of aerobar-mounted hydration. I took an in-depth review at their Aero 20 product, which is both easy to use, and tests very well in the wind tunnel. See the article for a link to their wind tunnel data.
The Speedfil A2 is here, and it's trying to be the best of all worlds in front-mounted hydration. Hit the review to see whether the effort has paid off.