Finally completed my clean up of the movies in my NAS.
Using Ember Media Manager, I had cleaned up my English TV serials and this evening, I completed the clean up. Ensured good poster sizes, accurate movie info and actors info, big and nice fan art etc.
Ran the scan in XBMC installed on Apple TV2 and surprisingly it was really quick. Took about only 20-30 mins for my several hundred movies. Guess it is due to the fact that it is just reading local info via NFO files. The advantage of preparing your data locally on the NAS instead of scanning.