I must agree with those who feel the iFly is an excellent product at an excellent price. In particular, because of the depth/breadth and reasonable cost of the chart update subscription. There are certainly other options that work and those who feel compelled to use them should.
I guess an old chart is better than no chart. However, at this price point for updates I cannot imagine that anyone would could be so cavalier as to fly with out of date charts when the up date process is brain-dead simple and available.
Having investigated a number of small plane crashes it has always troubled me to find out of date materials (charts, plates, manuals) in the wreckage. Holding up the prospect that insurance may not cover an accident if out of date materials are found may not be too important to most. I can't say that an out of date chart has ever been the cause of any accident I investigated either. But, I can categorically say that the attitude that the accident pilots had to preflight planning and preparation was usually evident in the care they took with having current charts, plates, manuals, inspections and so on.
It would seem common-sense to address every reasonable eventuality (and even some not so reasonable) while still safely on the ground. Once in the air it becomes more difficult. For a day vfr flight in clear, cloudless conditions over very familiar local terrain it may not make a lot of difference. However, trying to pick one's way through or past a line of thunderstorms in unfamiliar territory and remaining as certain as possible of one's situation above the ground in relation to airports should one need to get on the ground or refueling stops should the deviations or winds require an unscheduled fuel stop or remain over night, I find current chart/plate information one of the best insurance policies I can buy. And at this price it is a no-brainer. Add low ceilings, night or an inflight maintenance problem and it becomes quickly clear that one wouldn't want to have doubts about where one is or what frequencies were needed for navaids or radios. Flying single pilot IFR in IMC with turbulence over the Appalachians while trying to unfold and refold maps, communicate, navigate and aviate without an autopilot is a challenge I have met. It was not particularly fun. I did that with Loran and later with early GPS as well as VOR/DME. I must say that the prospect of having all the information that the iFly has literally in the palm of my hand and readable both day and night makes the prospect significantly less challenging (scary). Today, with limited real estate in the cockpit of my RV4 I am even more pleased with the small size and great power of the device.
I work with many business jet operators who are moving to an electronic flight bag (yes, often based on the ipad.) I am type rated in several jets and would like to point out that one of them, Bombardier's Challenger 605, has two small screens, one on each side of the cockpit and about the same size as the iFly that provides charts, plates, checklists and such to supplement the Proline 21 with its 4-screen EFIS and Collins FMS. it's great to have.