Dongles are useless for iPhone. You can only use them when the phone is in your hand or on the table. Not when you're moving around - unless you buy a new backpack "Made for iPhone" to prevent the lightning connector from breaking the moment you bend it slightly in the wrong way.
As much as I am pro lightning connector sans headphone jack, this is probably the most compelling argument I have read against it. It's gonna be interesting to see how that pans out. Mechanical issues that constantly break or damage the phone / headphones could become a massive issue for people.