Lucky The Fox said:

- Ability to build tanks without inventing the wheel (That is, the flexible tech tree.)
I don't think the system is going to work like that. One big thing is that that doesn't make any sense. Here is what the pre-release info section actually says:
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The Technology Tree, just like its technologies, is smart and flexible. You will have the ability to research different things, but they will lead to the same level of technologies. It will offer unique paths to guide your empire along. There are no longer static eras, as in Civ IIIs case.
There are different ways to discover technologies, like the already mentioned Great People, and probably by the Tech-Trees flexibility itself
You will also be allowed to skip whole branches of the Tech-Tree if you wish.
Moving up the Tech Tree will also unlock Civics options like Freedom of Speech and Slavery, which will have far-reaching consequences for your entire domain.
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Read between the lines. What I think what they were trying to express is that you can skip SOME traits that you don't want that aren't necessary (If you remember in CivIII, they had those little circle with a line through it in the corner of boxes with technologies in them that meant you didnt have to research? Example, Democracy was one of them, and there was the whole branch in the middle ages that led researched cannon, the Military Academy, and Cavalry (The only reason we dont notice it is because everyone usually researched it to get better units)). If you look closely at the info we are pre-release info section, you will see that technologies "require" other technologies, and "lead" to others.
Example:
Agriculture or Hunting>Animal Taming>Horseback Riding (Stop, Horseback Riding doesn't lead to anything else, as we know now of right now)
So at least for some, this is good news. But the bad news is that the Technology Tree will still be very close to what it was in CivIII with only a few changes. I remember someone saying that CivIV was 1/3 old stuff, 1/3 changed stuff, and 1/3 new stuff and that is why these games stay so popular over the years.