This info should be really usfull for people planning mods for HL2 and is taken from www.bluesnews.com
ALL objects in the game world are affected by the physics
Movement speed of HL will be retained
Drivable vehicles in both single and multiplayer
Engine technology scales based on your system specs
Known locations: City17 in east Europe, a harbor, a jail, the suburbs, a dried up ocean, an icebreaker (large ship)
Multiplayer is important and multiple game modes will be supported
The editor is called 'Hammer' and will be included, sounds like a complete development environment for maps, mods etc.
TF2 will be using the HL2 engine, once they decided to use the HL2 engine they stopped giving information as they didn't want to blow anything relating to it. TF2 will 'arrive soon'.
Of course, Hammer is the same name of the current Half-Life editor (formerly known as Worldcraft), so that's not really a surprise. And it's been established before that TF2, HL2, and Counter-Strike 2 are all using the same engine.
If you haven't seen them already, upcoming issues of PC Gamer, Computer Gaming World, and Computer Games Magazine have Half-Life 2 features. The magazine embargo (which was broken anyway) expired today, and while we're not quite sure when reputable online sites can start posting their previews and better-quality screenshots, we're guessing you may see some pop up by the end of the week.