I'll say it one more time... actually finish the game, then announce the release date.
I don't think it was Valve's fault. I imagine it's Vivendi that want the game released closer to xmas. And the problem would have been that with Valve's status, they will have signed up Vivendi a while ago, long before they had an idea of when HL2 would be finished, with a design to release it when it's ready (ergo, no release date in the contract). Vivendi, obviously wanting to nab what will likely be one of the greatest games of all time, agreed to this (not normal practice for publishers to agree to titles without at least a rough release date and a maximum release date).
So come completion time, Valve assume they are going to release when it's done and set themselves Sep 30th for that day. They most likely had the game completed about 4 months ago and are undergoing final testing and polishing until the day it goes gold. When Vivendi found out that Valve wanted Sep 30th, they will have decided that they could wait another 6-8 weeks and get a release during the holiday period - a much loved time for publishers (see a previous reply of mine to this thread). Valve will have entered into negotiations with Vivendi to set the release at Sep 30th. Vivendi will tell them where to stick it.
Now here's the shitter - Valve are in too deep to find another publisher. If they cut away from Vivendi now over something small such as the release date, Vivendi could sue them for millions in lost earnings. You see, without a contractual release date there is no breach of contract and Vivendi basically have Valve by the short and curlies. I have no doubt that Valve will have argued the deal right until last week, where they realised that even if Vivendi turned round and said yes to Sep 30th, it was too late to go gold and get it on shelves by then. So now Valve are royally butt-f***ed and have no choice but to leave the release date to Vivendi - which is why their statement about the delay was very vague about the new release date.
The problem with the games industry is that developers have no power at all about release dates etc. Publishers have all the power and the developers are their bitches. And the real shit on the cake is that Valve will cop all the flak for this. Everyone blames the developers for the publishers bullshit.
This comment was edited on Sep 27, 18:43.