I haven't read all the posts in this topic, sorry, but I have always been able to skip tracks through Spotify since my first Audi, which was a first generation A1 TFSI with a few options, one being tech pack high. I also have tech pack high on my current S3 and have never once experienced any playback issues. I am able to seek forward and back in tracks with ease and it doesn't jump around when I stop, skip tracks forward and back and this also abides by the apps shuffle rules, whereas others don't. I do find the MMI on the S3 to be exceptional, vastly improved compared to that of my A1. Seek functionality was very unreliable on my A1.
I have always connected my iPhone to the car via Bluetooth and have never used the supplied cables from Audi, as I used one with my previous iPhone and the lightning adapter on Audi's plug and it caused damage to the phones internal charger mount, so it wouldn't charge anymore.
Edit: remember hearing my dealer tell me my MMI was updated last time I had some warrenty work done. Although it did function as described above before this update.