I have been using the new UI for all of my games for several weeks now, and it is really starting to grow on me. When it first came out, I hated it like many on the forums. The developers acted remarkably quickly to deal with many of the complaints we put forward, and I would like to first say that I really appreciate that effort on their part.
One issue I still have with the new UI is that the colors, even with the saturation increased, still look rather washed out, especially compared with legacy mode. While I understand that this may be a stylistic choice, I am color-blind and so it is sometimes extremely difficult for me to tell the difference between multiple washed out shades of blue, or white, for example.
My suggestion is that the developers add some sort of graphics option which allows us to determine our own saturation levels or perhaps even turn on/off certain visual effects. The tactical armies change was a massive improvement, I would like to ability to scale up or down the resource icons, and the small 3D models which show which improvements have been built in a given territory (railroad tracks, factories, etc).
The new UI has come a long way in just a few short weeks, and I have been genuinely impressed with how much work they have done. I would like to see slightly more customization options with how it looks though. Right now, a saturation slider or even just an option to turn on high saturation would be wonderful. But in the future I could envision multiple different ‘skins’ that people could choose to play with that make the game look a certain way. (Especially if they allow us to use rectangular flags again instead of the horrid circles!)
Feel free to comment what you think. Thanks again to the Devs for acting so quickly on our feedback. The recent changes have me feeling much less of a need to open legacy mode.