An iPad and a well designed survey can change all of that, making the process quicker for the respondent, easier for the field worker to approach people, and making the data much more streamlined for the analyst at the end of the process. There used to be one other positive: people used to love to play with iPads when they were still new, but that advantage has evaporated now the novelty factor has worn off.
The iPad Mini is almost the perfect field device for data collection. The size is right: it's easy to hold and the weight never becomes an issue. Even clothed with Apple's Smart Cover, the easy of carrying never gets old. (P.S., if you are going spending an extended period of time with an iPad outdoors, always use a cover. Outside the familiar confines of home, accidents are a matter of 'if', not 'when'. Trust me, when you trip over uneven pavement and your iPad goes flying, you want a cover on it...)
You might ask why the iPad Mini and not the equally capable Nexus 7 with the supposedly flexible Android operating system. Therein lies the rub: for all of virtues of the Android platform, applications is still not an area where it exceeds iOS. This is the platform that the research contractor used, and I'm sure that a lot of other firms use the same survey software. The other advantage to iOS is the sheer familiarity of the device; you need to train volunteers on how to work with the survey software, but you never have to train them on how to use the iPad because nearly all of them use iPhones. This is a key point in a volunteer environment, as the workers typically come from either the fairly young or the ranks of the retired; you want to use something that everybody understands right off the bat.
The other problem with using an Android device is that the 7" 16:9 form factor is too small for presentation work. The iPad Mini is just large enough for a short presentation, but if you are doing anything involving design or graphic arts, the full sized iPad is the better choice. That would also be true of the 10" Android tablets, but we again run into the issues of user familiarity and software availability.
Apple people go on about how the 4:3 screen ratio is better than the 9:16 ratio of Android, and there is no getting around it; it's true. For the layout of text (important if you want to recruit strangers into five minutes of survey taking), there's no getting away from the fact that the iPad's form factor is better. However it's not all roses. While cleanly laid out, my feeling was that the application wasn't quite optimal for the size of the iPad Mini, as it was first programmed on the original iPad. It's not that screen presses are difficult, it's just that they require more deliberate presses when you are moving quickly. When you are going at a leisurely pace, the radio buttons and drop-down menus look perfectly fine, but if you are keying in something quickly, there's a tendency to trip out more than usual. I don't find this to be an issue with the smaller size of the device compared to the original iPad; it's a user interface optimization issue, not a hardware one.
The big question for Summer 2013 is whether or not the next Mini will have a Retina-class screen. For the purposes of doing real work, I would say that that isn't the most pressing issue; a bigger usability issue for me would be to increase the brightness of the screen, as clarity isn't that big of an issue on the iPad Mini's screen despite its low resolution by today's standards. Screen brightness is an important workability issue when you are taking the device outdoors or into brightly-lit conference settings.
Battery life never became an issue for us. Over four hours of continuous use, the devices typically went from full-charge to 40-60%, depending on the user. (Some volunteers were keen to click off the screen if not in use, others kept it on and let the screen time-out on it's own). Longer would be nicer, but it's not a weakness with the device.
I found the 16gb minimum of the first generation iPad Mini to be parsimonious even back when it was launched, and would hope that the second generation would have 32gb as a minimum. As it stands right now, for personal use I find that 16gb for commonly used apps and 16gb for music and video is just about right; not a lot left over in terms of free space, but moving up to a combined 64gb would still be overkill. However, for field work, storage was never an issue, and the availability of Wi-Fi everywhere nowadays means that data can be moved off the device and centralized quickly.
Looking into the future, it will be interesting to see what the next iPad Mini brings. The screen resolution will be a sticking point for sure; since iOS has less wriggle room with different screen resolutions than Android, it's either the current generation or a 2x multiplier for four times the number of pixels, which brings with it a number of technical challenges. However, the current platform works quite well in the usability department, and my hope is that the iOS7 upgrades that have been previewed so far continue with that.