i started NV all over again about an hour ago, finished the tutorial, and went straight for the HELIOS ONE building, finished that quest, making sure to pick the "emergency output" power level, and went back to ignacio, or whatever his name is, and picked the option that ended the quest. normally, u can pick that option as many times as u want for 325-350 exp, and 2 stimpacks and doc bags, but it only worked once!!!!! what happened?!?!?! did they make a patch that i didn't download but somehow still worked?!?!
I believe every exp exploit has been patched, well at least the majority of them anyway. There is nothing stopping you from deleting your cache however, and you can use the exploit offline if necessary.
I used exploits on FO3, and vowed never to on this one. Much more enjoyable just levelling normally.