What to expect with the Motorola X Phone, and is it a real game-changer?

Definitely the Customization Center would be a game changing feature. You could have the option between having a pure stock experience with little to no delay in updates, or a manufacturer skin with more features than stock but delayed updates.

Snapdragon 600, Tegra 4, or Snapdragon 800 w/ 2 GB RAM

4.7-5" 1080 S-LCD3 or Colorboost display, covered with Gorilla Glass 3

Kevlar body with a steel frame for more durability and splash resistance

3,500 mAh battery

All in a sub-9mm package would be absolutely fantastic. As for software;

Option between stock KLP or KLP with Motorola's custom UI via Customization Center.

It brings everything together; build quality, performance, battery life, durability, and enhanced customization with better software updates.

If Motorola and Google release this on the Play Store for >$500 off contract it would be a steal. Also, make it available on all major carriers, with LTE compatibility. Would be perfect :)