Played through a game as Austria yesterday, no serious bugs. The initial (first contact) diplomacy window with Bulgaria had no text, just the "There shall be peace in our time" etc. options. Haven't read through the thread so I don't know if this has been mentioned.
Other notes on the game:
- Germany was very weak - they peace vassaled to me halfway through the game. Other than Salzburg flipping to me I didn't take any of their cities and I don't think they were warring with anyone, they were just kind of limp the whole way through.
- Poland and Venice also wound up vassalizing to me - Poland after they DOWed me in the late 1500s - I took Krakau and Halicz from them and that was that. Venice peace vassaled to me shortly after the Ottomans spawned and started to obliterate their cities along the southern Adriatic.
- Speaking of the Ottomans, Holy Crap I think I know how the real life Habsburgs felt. The Turks had obnoxiously large stacks of cavalry and I was basically the sole bulwark keeping them from conquering all of Europe. They didn't manage to take any cities from me, and after beelining Kurassiers (my new favorite UU) I managed to take southern Serbia and Ragusa from them. After 1650, the next century was basically spent fighting Turks to a stalemate in Bulgaria. The Byzantines collapsed in the 1200s; I have no idea if the large number of independents in Anatolia made things easier for the Turks, but I assume it did.
- I did manage to get the first two UHV conditions, but the defensive pact one screwed me over - I had pacts with Spain and France for most of the game, but France wound up becoming a peace vassal of Spain, leaving me with only one pact. No one else liked me enough to sign one.

- The English buffs are clearly working as they were the strongest non-Muslim power. I believe they had a pact with the Ottomans so I spent most of the game at war with them, but Austria is landlocked and far away so it didn't really have any impact.
- The Burgundians held their own against France and eventually passed them in score. Both France and Germany, the two civs people always complain about being overpowered, were really lame in this game. Strange...

- Austria spawns as the Mongol invasions are winding down so I don't know what exactly happened, but the Kievan Rus survived them handily and then thrived thereafter. They were the strongest civ for quite a while until the English/Ottomans (and myself) started to catch up. I had to DOW on them early to take eastern Transylvania for the first UHV condition.
- The Cordobans survived until the end, although they were Christian. Portugal was double-teamed by them along with Spain shortly after spawning.