Un-freaking-believable!
The patch (v1.1.1?) broke my game, FNV won't start. Steam did the update when I wasn't looking, didn't have a choice to update or not.
So I verified the files - 146 files failed to verify! What!!
No I have to download 128Mb of something, I don't know what it is.
[EDIT] ...a couple of hours later.
The download was the C++ Redistributable and the DirectX installer which I had deleted because it had been installed and I didn't think I needed to leave all those files on disk. Stupid me! Next time I won't think.
The game refused to run as long as the "ArchiveInvalidationInvalidated!.bsa" was listed first in the archive list in the .ini file. Moved "Voices.bsa" in front of it in the list - game now starts. I'm still not absolutely sure the meshes and textures are being properly overridden, new textures and new meshes are no problem, it's the replacement textures and meshes I'm concerned about.
An interesting find: Something was put in the FalloutNV.exe file to change the display model for the Weathered 10mm pistol (if you have the ClassicPack). Previously if you tried to mod (like adding the silencer) that pistol would cause a problem - a missing texture would cause a big red exclamation point to envelope you. Now, if any mod is applied to that pistol, the mod is installed but NEVER displayed thereby avoiding the missing texture problem. I wondered if the mod was actually applied. If you put a silencer on the Weathered 10mm pistol it is indeed installed and the gun is silenced but you will NEVER see the silencer. The same applies to the other possible mods for that pistol - all the mods can be applied but you don't see them. No amount of fiddling with the GECK will restore display of those mods so something was put in FalloutNV to suppress the display. Possibly making a "clone" of the original model could restore the display of the mods.