Here are some old and new bits from The Witcher forum (some were translated from the Polish one).

Technical stuff:

Żbiku (3D Programmer):

• 
  As of today we assume that the video card should support at least PS1.1 and VS1.1, so the game won't run on GF2/GF4 MX. Maybe it will eventually change, but we recommend you to use cards which support PS2.0, on which The Witcher will look just as we planned.
  
  Actually, pixel shader can be emulated on every card, even 3.0, you just need to choose the appropriate device when initializing the DX. The only problem is that in that case everything goes through software, and it works so slowly that you are not only unable to play it, but even the menu will be unusable .

Inventory management:

Piotr "Fallen Zen" Panasewicz (Community Specialist):

• 
  The Witcher won't be able to carry everything. He doesn't have an endless backpack. He'll have a slot limit. He won't get burdened cause he can only carry small objects (no carring in the inventory of ten axes, 5 swords etc.). We're trying to make it somehow real.

Michal "Mike" Kicinski (Studio Director/Producer):

• 
  Armor is not that important for witchers, they use only light versions of them. In the game itself it will work this way that you can have one armor at the time (generally, armor = 1 piece). So if you get new one you have to leave old one. However, You'll be able also upgrade armor by adding better parts to it, but this kind of upgrades really doesn't happen too often.
  
  Also, most of the changes/upgrades are connected with completion of the quite big quests. It will be definitely hard to find excellent armor just lying on the floor in ruined stronghold...