If I had to guess, the speed of ordering will depend heavily on how custom your order ends up being.

I order items without cheese, which tends to take longer with cashiers anyway, who tend to assume you really mean you want it with cheese even if you say "hamburger". And there's about a 25% failure rate for the "no cheese" directive to be followed anyway.

But I reserve the right to (really) pass judgement until I've actually experienced a kiosk! Hopefully the UI is logical and doesn't hide options. (The current trend in menus seems to be bigger pictures and fewer options shown by default, while there are items that are still available but hard to find. Used to be able to look for "Dollar Menu" but now "value items" are kind of scattered throughout. Just finding the price of french fries seems to be a challenge for my feeble mind sometimes.)