There were reports last week about the impact that the Pizza Hut iPhone application has had on sales with claims of sales of $1M dollars in the first three months.
It's not obvious whether these are net new customers or sales are simply being transferred from other channels like the regular telephone. I would be curious to see if there's any bias in the time distribution of orders (it's easier to order a pizza via app rather than by phone from the back of a taxi), or order composition (the after-bar feast, for example). I suspect iPhone users themselves have subtly different tastes vs the population so that introduces bias there also.
Regardless, providing easier ways to order your products and services is rarely a bad thing.