My friend was on Provigil for a while and when "Nuvigil" came out, (or soon afterwards) his doctor recommended he switch from the Provigil to the Nuvigil, and the doctor also JUST HAPPENED to have some sort of special discount card to go along w/ the Rx for nuvigil....
-my thinking is, there was no medical reason at all for the switch, and this doctor was somehow benefiting from writing Rx's for Nuvigil when they were filled using the discount card....but I'm the paranoid type when it comes to Dr.'s and their motives behind the drugs they prescribe.
TO ANSWER YOUR Q'S:
No worthwhile effects after balancing the pros and cons concerning, motivation, concentration, or focus.
If you've tried Provigil at the 150mg+ dose range, then the effects are pretty much the same, except that Nuvigil gave my friend worse headaches than did Provigil, and the Nuvigil was much more "jittery" compared to Provigil
Provigil / Nuvigil are just like REALLY strong cups of coffee, but in terms of usefulness as a study aid for example, are only good for keeping you awake and don't increase those areas of cognition you're wondering about.
BUT, my friend has also taken the whole array of ADD meds so compared to ritalin or aderral, Provigil and Nuvigil were unpleasant and unsatisfying....
HOWEVER, if you've taken Provigil and found it to be beneficial then you'll be happy with the Nuvigil, you may get more unpleasant side effects so unless the Nuvigil is really cheaper stick to the Provigil...
Good luck