[Phoenix-D]

Features that aren't just "oh, shiny!":
-Limited LOS and having to survey new systems (leads to a problem with the game not remembering enemy units, like in SE4, but there's a settings.txt line that mostly fixes that).
-Greatly expanded modding possibilites- take a look at the date files.
-Combat. Warp-assults especially will be much more interesting: ships don't appear all at once any more! they come through the WP in a steady stream. You can tell them to go through all at once, but that risks losing some to interpentration.
-research is better, and points carry over
-contruction carries over; you can build multiple ships per turn, and multiple TYPES of items per turn.
-many of the menus are very customizable and sortable
-Alliances
-The treaty system is no longer fixed to a few treaties- you can include whatever you like in any treaty. Don't want to let your treaty partner colonize in your system? You can forbid that. Want to share intelligence, but not research? you can do that.
-the log has been improved. You can see diplomatic messages you sent, and those the enemy sent from previous turns, for example.
-Strategic combat has been improved- you can pause it, run through at different speeds, reply, etc.
-path.txt is no more. Looks like you can select mods in-game.