The usual caveat applies: no support in IE for the next ten years. I would love to have that date picker universally supported now.
to do otherwise just adds more work, not only for detecting the browser, but for making sure the page layout and so on works in both versions.
Personally, my strategy is simply to not write HTML or CSS. I write to a DSL that is implemented based on what browser is being served, so there are no sniffer scripts in the pages themselves. True, this does mean the same, otherwise static pages, may need to get generated over and over, but this is where caching comes in.