New Races
As we suspected:
Gray Orc
Yuan-ti Pureblood
The Gray Orc models weren't in the build yet, but the Yuan-ti had scaley skin on the models, although those models weren't totally in yet either.
New Classes
As we suspected:
Hellfire Warlock - Prestige Class for Warlock (has some really cool sounding special abilities, to be revealed later)
Doomguide - Prestige Class for Divine classes (Kaelyn the Dove may have been a Doomguide of Kelemvor, although she didn't technically have the PrC when you gamed with her. Therefore, taking the Doomguide PrC guarantees that your character will have a really sexy voice.)
Swashbuckler - Base Class (covered in detail elsewhere)
Party Creation
You can create up to 4 characters to permanently be in your party (i.e., they don't leave based on story). You can create just one character if you want, but some of the battles may be too tough for just one PC. I think a Dev said somewhere in this forum that the encounters are not scaled to your party level, so 4 party members may be advisable to survive.
You can create for your party a Party Name, Party Motto, and Party Biography. See the pic:
New PCs Start at Level 3
What this means is that all brand new PCs are granted a free 4,500 XP points. You get to level up the PCs once you create them to make them into whatever build you prefer. Get planning.
Party Conversation
The conversation system allows various party members to participate in the conversation. Basically, conversation is the same as NWN2, but now you have multiple party members shown to select from to see what their conversation options are. When it's the party's turn to talk, you can click on each party member to browse their specific options in the conversation, and you can decide who will speak and what they will say at each conversation branch. Sometimes certain characters (presumably depending on their class, race, skills, feats, etc.) will have unique conversation options that others don't have.
In the picture below, note the 4 party member icons just above the response options. If you click on each party member icon, the conversation options change to match that PC's options.
Overland Map
The OM pretty much behaves as a regular area would, except that the zoom-out is locked out far, and you can't pan or rotate the camera (it's like you're looking down on a map, which is the point).
Running around the map, lots of fun stuff pops up. If you have the skills, you'll be discovering things all over the place, like caves, NPCs, monsters, ruins, treasures, etc. It's quite fun to run around the map trying to find everything you can. In the various minor adventure sites available to visit on the map in the demo, I could tell that most were optional to explore and could probably be skipped, but those areas seemed to each have a unique and worth-while treasure in them that could help down the road in the game (like unique armor or other magic items).
As you get close to monsters on the map, you get a Survival skill check to stay hidden (like stealth). The longer you linger on the map, the more monsters that will be passing by. Also, the longer you stay "close" to a monster, the more Survival checks you have to succeed at.
Depending on which character you're running around with, the skill checks are based on that PC's skills. You can switch the "leader" character for the OM at any time, and then that PC is the one who is used for skills checks. The speed of party movement on the OM is also dependent on the speed of the "leader" PC at the time. A monk PC moves noticably faster on the OM, saving time, and potentially increasing the chances of evasion of monsters by moving by them faster.
Once a monster catches you, or if you go up to the monster, you get some options, like "fight", "flee", or "talk". When you fight, you go to a special "regular" area to fight. If you try to leave the fight area before killing all the monsters, you get a chance to flee to escape.
In the pic, the 3 icons at the bottom of the map are "Time" - shows current time of day if you mouse-over, "Game Menu Options", and "Rest".
There's lots of other really cool stuff that can't be revealed yet, so keep watching the forums and interviews for more details. I'm really looking forward to SoZ and some of that old Baldur's Gate style exploration.
***Disclaimer: Storm of Zehir is currently in development, and as such, all features are subject to change or removal before shipping***