If you haven't used high resolution texture packs before (in Fallout 3), they make things like the ground, walls, floor, wood and some other things look more realistic. They really change the feel of the game and I can't play it without them.
An example of the difference between a high resolution texture and a normal texture: http://www.fallout3nexus.com/downloads/images/12056-2-1270557414.jpg
A few thousand people are using these hd textures and I haven't seen any issues because NV uses a lot of the exact same textures as Fallout 3, pixel for pixel, it even uses some Megaton textures still labeled as Megaton. Using the high resolution textures makes the game look awesome. Check them out if you haven't already.
