- More adjustable arm rests (they go back and forward too)
- New mesh material which is apparently more supportive
- New back support mechanism which is a combination of the two previous options (which you could not put together) - both the lumbar and the pelvis supports
- Chair is angled 1.8 degrees further forward
- Tilt mechanism causes the chair to hug your body more, with less latency
- A new white-ish color option
Other than that it looks the same.
I'm in the middle of an assessment of both Aeron and Mirra 2, so yeah I've been in the details a bit too much this week...
...as a programmer I find it easy to make decisions based on facts, but when it's a decision based on how something feels, I lock up in panicked indecision and almost always make a choice I regret!