I suppose the previous videos weren't room enough to quench gamers amongst gamers who wouldn't come to grips otherwise... or that it was just a subject of circumstance? In regards to the actual news post, two new 720p Half-Life 2: Episode Two gameplay videos, which shows even today that the Source Engine can work wonders with a new render-to-texture super-sampled soft shadow w/self-shadowing system, 64-bit non-linear gamma-correct FP16 precision SM2.x/3.x HDR filtering/blending and then dynamic tone mapping... not to mention an excess of post-processing pixel shader light bloom effects otherwise, and then the new DirectX 9.x SM2.x/3.x particles system to accompany such.
The videos reveal the differing locations, weapons, vehicles, and the aforementioned Source Engine improvements. Weighing 157.1MB / 91.3MB respectively, be sure to make off to Worthplaying for these rather prodigious downloads (hinting at those still on 56.6k dial-up modems ).
(EDIT: and now 3rd one has taken a stride and is revealed, weighing around 125MB and can be seen at Filefront. And now the 4th one.... reveals itself as the masses find it better.... on FileFront, weighing 145.27MB..... and now the finality of the 5th one, as such can seen on Steampowered)