The problem with additional scenes is that any character development done is quickly forgotten any new characters introduced are forgotten or killed (except in bleach with those 3 mod souls) so it is a rather large waste of time and takes away form the main point of the overall story.
That being said i can see the use of some additional scenes so the writer doesn’t catch up to the manga. However i just wish it wouldn't involve garra using the same attack over and over with dedria responding to this with the same attack for 2 episodes additional scenes can be done tastefully and this is where the anime is lacking not that they do these scenes its because the new scenes suck and feel like time wasters
The writer of the anime sometimes ends up contradicting himself because of the extra scenes and this ends up pissing the viewer off. or they are just left wondering WTF...
Point is i don't mind additional scenes its just that naruto is failing to do good addtional scenes IMO