The bigger story for me is that Valve has managed to once again troll its fans with a "3" announcement. This is starting to have flavours of Stockholm Syndrome.
If they wanted a launch title that would drag in the biggest market, I reckon Left 4 Dead 3 or Portal 3 would pull in more people (both had large mass media marketing campaigns and are more recent). Or hey, all three ;)
The "worth the weight" thing is a joke. Theres an urban legend that says that the HL3 release gets postponed by 1 month every time someone makes a joke about Gabe Newell being fat.
