I definitely agree with this. The Panorama interview showed a very unattractive side of Diana, one that I think was better hidden or less developed before this.
I also agree with angelwngs that both Charles and Diana used the other. I don't really believe either of them intended to do so, or were aware of the fact, but I think they married for the wrong reasons and neither had much ability to maintain a healthy relationship: and as a result, the marriage fell apart pretty quickly. But I also agree with you, angelwngs, that Diana "played the game" well. Despite not being impressed with her as a role model, I have a bit of admiration for her ability to influence people. At its worst, it was deception and manipulation; at its best it was genuine compassion and personal magnetism.
When I do think about it, I guess I've come to see Diana's life as a kind of tragic waste (as far as any human life can be a "waste"). She wasted her own talents by choosing to focus instead on spite and self-promotion; and I think almost everyone in her life, at some point, used her (she was even born, supposedly, because Earl Spencer wanted a male heir and not out of any particular desire on the part of her parents to have more children). The royal family, including Charles, would rather have had a dutiful, emotionally stable princess than the real Diana; the media hounded her; and the public turned her into an idol. I really do believe that Diana (like every human being in the world) had many gifts, but I think even her good deeds are really outclipsed, in a way, by her trail of broken relationships and her tendency towards deception. I think if I had been on royalty forums while Diana was still alive I would have criticized her relentlessly...I know I didn't admire her at all at the time she died...but now, I feel sorry for how (relatively, despite William and Harry) pointless her life turned out to be, despite all the glitter and promise of the early 80s and her own capacity to be genuinely compassionate and unselfish.