Hi Skip et al,
First let me say I read through the whole thread now and like a lot of the thoughtful responses.
My approach from reading these books is not scientific and can be considered opinion. But, over the years I've read many books which each include several long case studies of people diagnosed with BPD. Some other examples would be James Masterson (Treatment of the Borderline Adult), Gerald Adler (Borderline Psychopathology and Its Treatment), Jeffrey Seinfeld (The Bad Object - this one has the best case studies, IMO), Vamik Volkan (Six Steps in the Treatment of Borderline Personality Organization), Peter Giovacchini (Borderline Patients, The Psychosomatic Focus, and the Therapeutic Process), David Celani (The Treatment of the Borderline Patient), and the books by Helen Albanese and David Roberts already mentioned.
These writers are in the psychodynamic camp of psychotherapy. They have worked a lot with borderlines, and they are realistic and pragmatic about how difficult therapy can be and how long the process can take. But they are also mostly optimistic, that if the person is willing to seek help and has the resources, outcome can be very good. I like their writing because there are many case studies, often about 10-20 pages long, where you get an individual borderline's full life-history, details on the course of treatment, analysis of their functioning socially and in work toward the end of treatment, and you really get a feel for the "borderline" as a person (in these books alone, there would be several dozen of these cases). Since these cases usually involve borderlines being in therapy for several years, it's hard to study things scientifically as with shorter term treatment. But, these writers have many cases which show borderlines, both lower and higher level, improving to the point that they are no longer remotely diagnosable as BPD - they often come to have good relationships, to stop being difficult and manipulative, to be able to regulate their mood pretty normally, to function well, etc. In medical language, they are cured, or in normal language, recovered and well.
I also know that this is possible (at least in my experience) because I was once borderline myself, but am not any longer. I went to intensive therapy for 6 years to get better, and I function and feel much better now than I used to, have better relationships, and am no longer manipulative or difficult to around (most of the time!). I have two friends who have severe BPD symptoms and who I try to help (and they found me because they were looking for help), and that's why I sometimes come onto online forums like this, to see what people are saying about the condition. I still feel there's a lot of misinformation out there, and a lot of pessimism that is unwarranted (in my opinion), although in some cases, yes the person is not willing to get help or acknowledge the problem, and at that time nothing can be done. But for BPD people who want help, I certainly would say the condition is fully curable, although those are overly medicalized terms. In the way I think about it, a borderline can gradually emotionally "grow up" and become an adult in an adult's body, rather than a child in an adult's body.