This major gameplay changer will alter many aspects of the game, to improve continuity, remove errors, and increase immersion. Thousands of variables...
All major textures in the game were increased to 400%+ of their original pixels, sharpened, and had some detail added. Then new normal maps were generated to take advantage of the greater detail, which results in a significant improvement over the original graphics. This enjoys 0% compression files, which helps offset the fact that larger files requires more system resources.
You can further compensate by reducing some of the Advanced graphics settings (as access by the FNV Launcher's Options -> Advanced tab). Reducing LOD distance, turning off Shadows (since the game engine does not use them anyway), and following the other suggestions from Tweak Guides (http://www.tweakguides.com/Fallout3_1.html) will help you get the most out of this pack. My dual-core can handle this pack easily enough, but if you have less than 4GB of RAM (total) then you might want to consider 4Aces FNV RegRes.
This mod is no longer under development and all aspects are finalized.