It's nice that these things have good audio quality, but it's ridiculous that they're needed at all. They should take these nice DAC/amps and build them into the devices, like they used to. It's a gigantic step backwards in usability to have to carry these tiny little dongles around in order to have the functionality that older devices had built in. What are you supposed to do with these stupid things? Carry one around 24/7? You'll lose it. Carry one hanging out of the phone/tablet? It looks ridiculous and it'll break. Keep it attached to the headphones? Then you have to buy one for every pair of headphones, or other audio device, and you can't play music on someone else's system if they don't have one.
The whole point of a smartphone was that it was a self-contained all-in-one portable device you could carry around 24/7 in your pocket and always have on you. It defeats that purpose if you have to carry a bag of accessories in order for it to function. I'm going to hold onto my iPhone SE and 6S as long as possible as they're the last ones Apple made with headphone jacks.
The only alternative to a 3.5mm jack that I would accept is if USB-C becomes the standard for all phones and other devices and also for headphones, and if it passes both analog and digital audio signals, so you use it with passive or active headphones.