The other mistake I've seen with the "mobile" and "tablet" mindset is that "desktop" navs that rely on hover don't translate well when the "tablet" is desktop-e

The other mistake I've seen with the "mobile" and "tablet" mindset is that "desktop" navs that rely on hover don't translate well when the "tablet" is desktop-esque in size. In general I prefer to presume the user is always touch-based. At the very least, that's their mindset / exportation. Personally, I get annoyed with desktop experience that use hover but don't make it mindlessly obvious that you need to use hover (to get the info I need). Clever might be clever but it's too often a shite UX.