http://www.youtube.com/watch?v=NMMf0EidJAc
Words cannot contain my excitement for the game after seeing this trailer. I don't think I'll ever need another one to play after this comes out.

Yes, the puzzles look awesome, I might enjoy this one. Didn't enjoy the first.

That looks ace. The Portal games (and L4D1, to a limited extent) are probably the only games I've enjoyed from Valve since the first Half-Life.

Do they know what they have done?

Made the slip & slide popular again? Valve will begin to sell a long sheet of plastic and a bottle of aperture science propulsion gel (aka: detergent)

It's funny how both of those games are made by companies that Valve assimilated.

Good to see another game with volumetric liquids. Trust Valve to actually make it useful. This is looking very cool indeed.

Let's hope there will be more cake this time....

True.

Funny in that it shows Valve are able to spot and recruit talent? Well, yeah, I suppose that is pretty funny actually given how lethargic their core devs are, and the muppets they let loose on Steam's forums and support.

Don't a lot of companies do this? Nintendo assimilated Rare and HAL during the SNES era, Silicon Knights and Retro Studios during the Gamecube era, and I think there were other studios. All of those studios made some of their best games during their time with Nintendo and then they were sold when they stopped being useful, except Retro that still works with them to this day.
EA has Bioware now, Activision acquired Infinity Ward, Zenimax bought ID software, etc. I think it is better when the whole studio is bought by a big publisher instead of they recruiting individual talent as long as the studio retains certain independence in the creative process.

They have been programming the new Steam client, adding features to Steamworks, and porting the Source engine to Mac and possibly Linux. Right now Valve is more interested in being a DD seller than a game developer so they buy studios that will make games for them, THEY are their core devs for game programming now. For all we know, Valve possibly doesn't even have any staff actively working on HL Ep3.

Nintendo's second party publishers also tended to work on Nintendo's own IPs, at least to some extent, Rare with Donkey Kong, Retro with Metroid, etc.

This is what I expect Valve to do eventually. They will probably give HL2 EP3 to the L4D team after they make L4D3 and everybody is sick of that franchise or maybe they will fire them.