A quick look at the Switch's Interface and Load Times
Nintendo Insider sliced out this moment from Nintendo's own Treehouse live stream. It shows a super clean and simple interface and reasonable quick loading time to jump into game (more like 10 seconds, to the Wii U's sometimes 30+).
If you ask me, the icons below look like messages, store, images, controllers, settings and power if I were to read them as a designer. Also it seems to have an account link in the top left, and the device is in airplane mode and with full battery.
It also seems like the games will be a simple list of squares. hopefully this will have some sorting or filters for those of us with large virtual console titles.
Also, Zelda Breath of the Wild seems to launch it's open world save file around 25 seconds or so after the file is selected. So certainly lengthily, but not huge when comparing to other open world games on consoles like Xbox One and PS4 like The Witcher, GTA V, and Forza Horizon.