Responsive design headers

Hi,

Just after some info on headers. Google recommends using a Vary: User-Agent (https://developers.google.com/webmasters/smartphone-sites/details) for responsive design. I’m just wondering if anyone is using this with w3tc and if changing the header will cause any problems with caching.

Thanks.

http://ww.wp.xz.cn/plugins/w3-total-cache/