Also not OP and I also have a Mirra 2. There is a school of thought that as the Aeron is a design classic they can't really iterate on it. The Mirra has been great for me.
Not OP but I have a Mirra 2, I liked it better than the Aeron or Embody. I do really suggest you go someplace where you can try it out, also the various sizes. I bought refurb, don't remember price.