I own the Sony WH-1000XM3 since last July, and I own some older wired cans (Sennheiser HD-600). I can honestly say that I was very pleasantly surprised by how good the Sony XM3s sound. I purchased them essentially for convenience, being able to walk around the house or in the woods without a cord around the neck — and they do just that, remove a chain on your neck. However, as I started to use them more and more, I realized that I really enjoyed the sound. I listen to my music (digital) mostly from SACDs or hi-rez Qobuz (studio), and the quality of sound on the XM3 is different from my Senn 600, but definitely not worse : to my ears, those headphones are as good as a lot of other wired headphones, and perhaps better than some. The noise cancellation thing (I hated this feature on previous headphones that I had) works surprisingly well, I think Sony really pulled a great trick with this unit.
I also use the XM3 for late night movies, and it works great with my Macbook Air. Unfortunately il I use a dedicated player (Cambridge CXU), it won’t connect so I have to use my Musical Fidelity X-Can v2 and HD-600.. and quite frankly for a movie or a concert, opera, etc, I don’t hear a great improvement over the XM3. So my advice with the Sony XM3 is to forget all previous (audiophile) points of reference and try them with an open mind. They are surprisingly good.
Note - I think I will soon test some in-ear alternatives such as the Cambridge Melomania for more freedom when hiking in nature or gardening
I have not upgraded the firmware, so I can’t comment on that point