Since I can't post comments apparently
---------------------
Just want to clear up some stuff on the Half-Life 2: Episode 1 thing.
Originally it was titled "Half-Life 2: Aftermath," and initial price statement was 12.99 (Though it has been speculated that it was the "pre-ordered" price, and it would be a 13 dollar preorder, 15 dollar normal price on Steam). It was always mentioned as being episodic though. (An article in the September issue of CGW even talked about what they're thinking about for the next episode.)
The original statement was that the would put out one of these episodes every three months (CGW article), but considering this is Valve, I'll be surprised if they stick to that release schedule, especially considering how long they've been working on Aftermath.

The episode was said to be "3-4 hours" "1/3rd as long as Half-Life 2" and "Around five hours" (Gabe’s FAQ) so I'm guessing mileage will vary.
Originally it was ambigious on whether or not it'll get a retail release or just be Steam only, but since then we've seen listing for a retail package that Valve clarified that would contain Aftermath, Half-Life 2: Deathmatch and Half-Life: Source Deathmath, for $20 bucks. This would be available by April 24th. (Teamkiller Article)
Now, the gaming press kept calling Aftermath an expansion and not an episode, which I'm guessing is what prompted Valve to rename it to "Episode 1." Personally I think the name pales compared to "Aftermath" but whatever I guess. Whether or not the prior information on Aftermath applies to Episode 1 is unknown.
Sources:
Gabe’s FAQ:
http://developer.valvesoftware.com/wiki/Gabe_Newell%27s_FAQCGW September 2005 Article: Not online, unfortunately.
Teamkiller Article:
http://tkv2.teamkilled.net/display/article/half-life-2-aftermath-platinum-price/I couldn’t find sources for the original price, nor a few of the length estimates, but since they’re probably out of date anyway, I guess that doesn’t matter

I hope you found this post useful
