If the HD Texture Pack stopped during installation it might be worthwhile re-installing it as I believe the data may be corrupted by this error. I've done this and was suprised by the difference and I got a friend who had had the same error do the same and he noticed the difference as well, another friend whose pack installed without stopping did the same and didn't see any change. I think if the game partially installs the Pack and stops, then starts again the data is corrupted.
You re-install by going into the Xbox menu, go to the system blade (far right), select memory and scroll to Battlefield 3, open the folder and delete the file called HD Textures.
To reinstall correctly insert the BF3 disc and start the game, wait till the loading screen with "Press Start" on BUT DO NOT DO ANYTHING. Wait until you hear the disc stop spinning (takes a couple minutes), once it stops spinning press start and then install the Texture Pack.
If you do try this and see a difference can you post here and let others know.