I haven't heard a difference from the upgrade on my Ares II. Denafrips confirmed I did the upgrade successfully, and said it may take time to "burn in" (really? firmware? I find that hard to believe, although the fact that the DAC had to be powered down to do the update could have a short-term effect until it warms back up.)
I've enjoyed a wide and deep soundstage from the Ares II before the upgrade; having Apogee Duetta II planar speakers helps in that department (even the height of the soundstage is excellent).
I've listened to familiar hi-rez classical Qobuz files from my Bluesound Node (the current version) and familiar classical SACDs and well-recorded CDs.
The rest of my system is quite high-quality if somewhat vintage, if you check out my system.
Congrats to those of you who have benefited from the upgrade. I am going to try an AudioQuest power cable with the Ares II--I expect that could make a clear difference that the firmware upgrade didn't.