Just downloaded and ran an older version (V8). As far as I can tell, all the typical features work (tech trading, vassalage, opinion, etc...), short of espionage. When I attempted to use my spy (playing as Babylon), it showed a bugged graphic for the nation that was partially the american symbol, partially a translucent white. Furthermore, none of the cities on the map appear, nor any of my own cities.
Currently running:
JFD's Soviet Union (Lenin)
Tomatekh's Xia (Erlitou)i
Quiet Diplomacy
Infoaddict
EDIT:
In further playing, it appears that the intrigue screen is also bugged, and nothing will show there (Earlier, Napoleon had informed me of Ashurbanipal's hostile intentions toward me). Furthermore, any further spies you accumulate will not be visible (I had entered the industrial era). As for the barbarians, they appear to have gone psychotic, with one swordsman running around between my four (9 tiles apart) cities before I shot him and put an end to his misery. Barbarians have been seen as landsknechts, one having attacked Dur-Kurigalzu.
Finally, the most aggravating, it appears that Civ IV Diplo Features overrides the beautiful (and quiet) notifications of QD.
EDIT TWO:
Continuing on, I notice that liberating city states is not permitted, with none of the options (Puppet, Annex, Raze, Liberate) appearing at all. Instead, I then got a city that I had hoped to liberate. Second off, you can only send trade routes to the first 3 city states you meet (tested with cargo ships), although others can send trade routes to you. It doesn't matter who has the city states (Assyria controlled Buenos Aires, I could send a trade route to them), or your relationship status (I was at war with them). You also are unable to send more than one trade route (tested with cargo ships) to a destination, even if you use different cities.
I hope someone shows how to make EUI compatible.
