This really got into some counting-angels-on-a-pin territory pretty fast.
I'd like to address a couple of points that were raised that might be useful in terms of practice rather than which "ism" one identifies with.
The first is the use of the term "dark night". I know, I know. It's a Christian term. In some quarters it's a pretty bad thing to use anything Christian, and I get that. However, this is actually a pretty commonly used term among people who have been through it. I picked it up from my teacher, and thought he came up with it until another teacher corrected me and told me that the senior teachers at IMS had been using it behind closed doors for years, and that is where it slipped into the common lexicon among buddhist practitioners. Perhaps it's an American thing. So if most people here prefer we could stick with the term used in the Vissudimagga: "dukkha nanas".
But that is more angels on the pin. Here is the practice issue: what are these things? For those who are interested in the direct reference (and from the conversations here I think a lot of folks are), you can read about them in the Vissudimagga directly at http://www.accesstoinsight.org/lib/auth ... on2011.pdf
However, the description of them doesn't start until the section labeled: "Purification By Knowledge and Vision of the Way" which begins, very ominously, on page 666. It is placed in the section of "Understanding" as opposed to "Morality" or "Concentration", and that speaks to another point raised here, which is this: why are these bad experiences part of the path if this is a path that leads one to let go of bad experiences? This is retro's point, I believe, when he raises the right effort issue.
What these are is a direct experience of the first noble truth, that is why it is in the "Understanding" section and not in the "Morality" section (where right effort is found). You need this first in order to let go of suffering. You can find info about that in the section on "The Three Kinds of Full Understanding", but I'll give the cliff notes here: first you understanding by "knowing" something (i.e. tasting it directly), second you understand it by "investigating" it (watching it arise and disappear many times), and lastly you understand it by letting go of it (no longer automatically seeing it as "me" or "mine"). When you go through the nanas you get a direct taste of each of the three noble truths: impermanence in the arising and passing, suffering in the dukkha nanas, and non-self in equanimity. The progress made through the nanas is essentially the process of letting go. You simply don't move to the next one until you have learned how to let go of the one you are in.
So, directly facing suffering and letting it go is a core part of what one does in insight practice. It's my personal opinion that it is also a core part of what folks are doing in other traditions too (hence the references to Christian terms and so on).