Only because it lacks a stylus.
In at least a few places in Aus (Canberra Centre, Melb Airport, Elizabeth St Melb) I've seen ipod touch sized PDA's being used to take down orders at McDonalds.. (including special orders - they got my mcflurry + caramel topping down fine).
Maccas may have a slightly limited menu - but it's still pretty large compared to some restaurants.