Good for both parties - Everton need a good manager and Benitez is a very good manager. His record at many clubs shows that he is imho a great manager. Everton fans need to get real and accept that he could turn them around and, with the financial backing Ancellotti had, push them from 10th into the top 6. I would put money on them now finishing better than their present 10th next season. Top 6 is the best they can reasonably expect but I wouldn't put it past Benitez to get there, and also to be canny enough to play decent teams in the cups to try to kickstart them with a trophy.
I understand that he never sold his home in the area so if he can make this his last job for the next several years, good for him.
Good luck to the toffees!