Elite Bastards posted a review on Half-Life 2: Episode One

It is thankful therefore, that the advent of their Steam distribution system has helped to persuade Valve to move away from producing major new games every half dozen years or so, and rather to make use of their existing (and ever improving Source engine) to work on episodic content, which can be released as small chunks of gameplay (typically five or six hours or so) as and when it is ready.

So, enter Half-Life 2: Episode One (formerly known as Aftermath) - The first episode of the continuing Half-Life saga which continues directly on from the events at the end of Half-Life 2. How does it rate against its predecessor? Four of Elite Bastards' most intrepid members - Jollemi, DarkJedi, baz8080 and Hanners - Journey back to the heart of City 17 to find out.

Half-Life 2: Episode One Review