One of the benefits of iOS devices is their ubiquity. What if a server spills a drink on the cash register? Then your register is fried and you have to wait for a replacement from the vendor. If someone spills a drink on an iPod Touch, though, you can run down the street to the Apple Store (or other vendor) and drop $300 on a new one (which you can return if you get the other one working).
The fact that the whole ecosystem (app store, iTunes, backups, etc.) is designed for consumers means that it's easy for anyone to deal with. It would be trivial to teach all your management and supervisors how to reset, restore, etc. an iPod Touch in the case of hardware problems, rather than having to log a support ticket with some company somewhere when the PoS hardware is being problematic.
Most restaurant/bar specific POS systems are water resistant for exactly that reason. I'm sure it that's happened though, that's why it's "water resistant" and not "water proof".
So lets say it happens to your iPad POS and you run down to the Apple store to get a new one. What happens to your data? Is it stored on the device, or is the backend hosted somewhere? How do you get your old data into your new iPad?
Another thing I just thought of... lets say there's a horrible bug that's causing some big problem. Wouldn't you have to submit a new version to Apple, which then needs to get approved by them?
All that being said, there's risks with any POS system since it's pretty much mission critical. When I launched my company and did a Show HN, some people thought it was a bad idea (it's web-based). There's a lot of what ifs you can bring up that all sound terrible to a business owner. I'm sure a lot of people will go with iPad POS systems, I'm just wondering if there's a good reason to or if it's just the cool thing to do.
The iPad is fairly water resistant at the end of the day, we've had a glass spilled on it (!) and it was fine. There's a database that the app allows you to email to yourself to backup, and you can connect it via iTunes and use Apple's ridiculously cumbersome iTunes methods of dragging files in and out. I'm not happy with it necessarily, but the attitude I have as an iOS developer is "let's see what happens in iOS 5 to make file management/sharing/backup easier, it *has to get easier...right? right!?"
Think of it this way - up until recently, POS systems were monolithic things that were never updated. Web POS systems take the opposite route of just throwing out what you have and fixing bugs as they pop up, which definitely is easy. With the App Store, it's sort of medium – we can easily ship updates, but it might take 7-10 days. IMHO, it's not a showstopper though. If it was, then almost no software would have shipped before the Internet. You just have to rely on the fact that you're a good developer, with a good testing process.
> What happens to your data? Is it stored on the device, or is the backend hosted somewhere?
That would be good to know since the data on the hard drives of POS systems are a target for thieves to the point of ignoring the cash and just taking the hard drive.
The fact that the whole ecosystem (app store, iTunes, backups, etc.) is designed for consumers means that it's easy for anyone to deal with. It would be trivial to teach all your management and supervisors how to reset, restore, etc. an iPod Touch in the case of hardware problems, rather than having to log a support ticket with some company somewhere when the PoS hardware is being problematic.