Unity and application development are not a fun combination. Their UI system is notably terrible in both performance (not only the redraw-every-fraction-of-a-se

Unity and application development are not a fun combination. Their UI system is notably terrible in both performance (not only the redraw-every-fraction-of-a-second paradigm, but just the plain ol' software architecture and layouting, or even simple things like culling offscreen elements) and features (Event bubbling/propagation? Naaah who needs that? It's not like you're putting a button inside another button! Or a button on a slippy map... Oh wait). And while the prospect of cross-platform is appealing, it has 0 accessibility support and no way of embedding or being embedded into native widgets. It's just a little bit better than passable for game UIs (non-interactive HUDs and one-screenful-at-a-time interactive menus), but once you start needing to implement things like drag&drop, virtualized scrolling, or non-trivial layouts, it get exponentially harder when compared to a "proper" application UI library. Believe me I use it for a living :)