Played some more of TW3K lately - I find the research tree probably one of the best ones ever made in a TW game. Almost all of the researchable technologies / reforms provide meaningful bonuses, which means that you're quite pressed to take a decision on which one to do first. Bonuses are solid, some of them great even, which is a stark contrast to some of the stuff that you got in Attila TW for example.

Also - the tree itself is gorgeous. Amazing UI.