UA strings have never been an accurate indication. If you're not using JS, then you probably have no reason to be sniffing the UA string to detect browser features, since most of those features are JS-related anyway.
It's an upgrade for the people who actually need to get an indication of the supported features and APIs of the user's browser. Otherwise, you should be using media queries.
One exception: you might want to user sniff IE and serve a completely different version due to all the CSS problems. (I know you can use IE-only comments too, but I’ve been in the situation where making a modern version simultaneously IE9-compatible was just too frigging maddening.)
Detecting dumb search crawlers, that don't support major features required for my webapp, and displaying a fallback splash has been the only reasonable way I've found.
It's an upgrade for the people who actually need to get an indication of the supported features and APIs of the user's browser. Otherwise, you should be using media queries.