Some of the new information includes details about the game's different classes and weapons, returning maps (2Fort and Well will both make a comeback), gameplay, and other tidbits. Interestingly, the preview says it would be technically possible to let PC, PlayStation 3, and Xbox 360 users play online together, although any final decision is reportedly up to Sony and/or Microsoft. Owners of PCs with multi-core processors can also expect "additional, undisclosed, graphics details."
The preview quotes a late September release time frame for the Half-Life 2: Episode Two "Black box", which will be a PC exclusive and include Episode Two, Portal, and Team Fortress 2. Thanks to Blue's News for the links.