HDR looks pretty in this short demo, though HDR will be present in the HL2:Aftermath sequel as will all future Source games.
Adds nice realistic touches to how your eyes would react in real life. If the current hardware supports it well i dont see any problems with Valve making their games look better.
The only problem would be speed at this point. the HDR is damned impressive, and Lost Coast - although short - is a very well put together tech demo with nice touches such as the developer's notes. DoD already uses HDR and it does impact the gameplay.
Oh and isn't Aftermath an expanion pack? as opposed to a sequel?
The HDR in DOD:S threw me off for a bit. There's nothing like running around a corner into gunfire, and being blinded temporarily by sunlight shining on a wall.