I think the main problems with PC's today are its cost, and barrier of entry. Peter said that a decent gaming rig could be put together for 500 bucks, almost double what a new PS3 is now. Also, the fact that it does have to be "put together." The average person cannot put together a PC from parts they buy onlne or wherever, and 500 bucks will hardly buy you shit if you buy something preassembled.
What Valve should do is they should release their own PC that would be underneath your tv, but make it super easy to upgrade. What I mean by this, is that there should just be a slot or whatever, where you pull your current graphics card out and put a new one in. It should be super easy to do. Make it compatible with keyboards and controllers, and allow it to function not only as a game player but as a full fledged PC, doing anything I can currently do on a computer. Games should still have scaleable settings, allowing for older versions of their "steambox" to run things on lower settings, but for people who do replace pieces of their Steambox annualy or biannualy they should run the highest settings, just like a normal PC. The only hurdle to this is making it affordable. Valve obviously has to exert its marketplace clout to bring manufacturers down, or make its own pieces. Valve just has to make it easy to do, and make it compatible with many PC parts, not only things that would be Valve branded.
I remember when I was younger I would always go to the library and look at their copy of Nintendo Power because that would be the only thing I would want to read. Good times.
AntiH3ro97's comments