I use the Sennheiser MM 70s in-ear headset with Jolla, mostly for listening to music, but microphone also works OK. Most pleasant surprise was the lack of background hiss. For example with Nokia E71 there was a lot of hiss with 16 ohm (impedance) headphones, but for Jolla they seem to be a great match. Jolla's headphone jack feels quite sturdy just like the microUSB port. Even if I turn the audio plug, it doesn't cause any interference.

On headphones' sound quality I agree with PCmag's review. The weak point of the product is the flimsy volume slider. Accessories include 6 pairs of different ear sleeves and a nice pouch with a clever opening mechanism. Cable length from the plug is 1.0 m to the left side bud and 1.3 m to the right side, for a tall person it might be too short.

A wired headset's button doesn't work in Jolla, but pressing the button does create kernel messages (dmesg), so maybe in the future functionality could be added to Sailfish. On some phones you can also skip tracks in media player by pressing the button twice, that would be a nice feature to have.