I've purchased the games individualy over the years. BTW, anyone still wanting just Portal, Steam has it for $4.99 via their store until January 2nd. 75%off!!!
I tried firing up the Bioshock demo, and really wasn't impressed with the coding. I don't have a "great" system, merely one that has served me well for almost five years and has been adequate enough with several upgrades. Bioshock requires an uber-puter and I'm not going to build a new one just for one game.
I can run all of the Valve games easily. They don't look fantastic, but they're playable and I have enough effects to appreciate the game quality. Valve knows their stuff and makes games that are fun, playable on most systems, have actually story to them, and keep you wanting more. Contrast this with companies that make a game with new water effects and force you to upgrade.
I think they succeeded at where Interplay wanted to go with their "By Gamers, For Gamers" philosophy. In the commentary for Portal, the voice-actress even admits she's not a gamer, but wants to play Portal because the gameplay intrigues her, as well as to get the cake recipe.
BTW, anyone interested in knowing what my ancient system is:
It's home built- P4 2.4GHz (started out with a 1.4), ABIT BD7II-RAID with a pair of Western Digital 80Gig drives, 1GB Kingston value ram, ATI-9800 card,Creative DVD-rom drive, and a Soundblaster Audigy OEM card. Oh..WinXP, of course.
This has been, by far, the most reliable board I've ever had, and my I-T friend says he's never seen one upgrade and survive like mine has. I'll be sad when I finally do upgrade from it. Maybe I'll make a cake.