I have not spec my toon and did not do any combat. Hence, I cannot comment on those and many already covered that area.
I am still in the maintenance mode and do peripheral activities.
The following is what I found so far:
1. The invoke for last day invocation is back. I have at least 3 characters got that this morning. I thought it was fixed. May be it was never fixed.
2. Upgrade enchantment requires ward to be present but that can be turned off in UI setting.
3. VIP id scroll becomes potion which is a great gold source (besides healing that I expect we will need a lot).
4. If you have duplicate character bound companion in mod 15, the duplicate companion goes to inventory and become account bound. I have many duplicate companion obtained from Winter festival and did not discard them until I needed the room in old idle companion slot. Character bound -> account bound. Nice.
5. If you have enchantment in companion gear, removing the enchantment does not require gold.
6. The UI windows is bigger. e.g. it could fit the inventory and bank windows within the screen nicely in mod 15. Now, I need to change the scale to 0.98 to be bearable.
7. Click on the buff icon gives you a bigger window to show all the buff.