While building Half-Life, we came up with several ideas for expanding the first person action experience. I don't think we're done with it yet. But there's no need for Valve to be limited to a single genre of games. We touched on a bunch of exciting things in Half-Life with story, characters, AI, and scripted sequences that we still have a ton of wild ideas about. I'm sure we'll be pursuing many of those ideas in future products.
Exciting times are ahead for Valve.
3rd vs. 1st person. It depends a lot on the game you're designing. The first person perspective seems more immersive. It offers some unique opportunities for involving the player in a story in a way that other forms of entertainment can't. It gives the player a sense of actually being there.