There are benefits to having a pure, native app. Quiver starts literally instantaneously without any lag, partly because it's less than 5MB(!) in size.
Here's a good read from the author: http://yaoganglian.com/2015/11/21/Quiver-3/
Yep. Speaking specifically about developing for OS X only vs. multiplatform, there are big tradeoffs to be made by taking multiplatform options outright. In my eyes, nothing is as great for UI-centric desktop application development as Obj-C/Swift paired with Cocoa/AppKit. It just works so well, and though Qt is probably the best of native multiplatform solutions it’s still not comparable.
Exactly. I used another note taking app, aptly named "Notebooks" (http://www.notebooksapp.com), which is built with Qt. It's cross platform, open data format, and while it sort of looks and feels almost like a native app, it just doesn't compare to a true native app like Quiver.