Also, the Borg he encountered in I Borg and Descent were individuals and not part of the Collective. This is really the first time he is dealing with I guess you can say the "real" Borg. The ones that assimilated him.
In First Contact, Picard sees his worst nightmares become reality. The temporal wake at the beginning allows him to see that the Borg have conquered and assimilated Earth. He finds out in this film that he is still connected to them by the fact that he is able to "hear" them. Beverly must have missed a few Borg implants or something in TBOBW part 2 when she removed them. That might have made for an interesting exchange between the two in the movie, but sadly was overlooked. Picard himself may have thought that he dealt with his feelings regarding the Borg in the past, but this film puts that to the test.