A new, extended version of the Episode Two trailer is now available for high-res download (or watch it below). Half-Life 2: Episode Two advances the 16-million unit selling franchise, as Valve’s trilogy of episodic single player releases continue the award-winning story of Half-Life 2.
Armed with new weaponry and vehicles, Dr. Gordon Freeman must race through a countryside riddled with an increasingly feirce Combine threat. Episode Two is coming to PC, PS3 & Xbox 360 in late 2006, and also includes Portal & Team Fortress 2. You can watch the old teaser here.
Visual improvements shown below.

You can expect new weapons and new enemies, of course, plus a rather fancy new Cinematic Physics system. It was invented by Valve’s Gray Horsfield; he used to work for visual effects facility Weta, and produced the destruction scenes in Peter Jackson’s King Kong and the Lord of the Rings films.

Thanks to classicgamer for the comparison screenshots.