Let me preface my remarks by saying that I have not read all six pages of this thread, so if someone else has covered this, I apologize. Here is my take on the LDS concept of Hell that I was taught growing up as a Church member:
I'll break down the three categories that Scratch laid out here:
--Spirit Prison: This is a temporary "waiting place". Since resurrection is a gift given to all by the Savior, all of us, saints and sinners, will be resurrected. Those who are judged worthy for Terrestrial and Celestial glory will await resurrection in Paradise. They will be at rest. Those who are judged worthy of Telestial glory will be in Spirit Prison.
--Outer Darkness: This is where the Sons of Perdition dwell. Only those who have a full and complete understanding of the gospel and deny Christ himself will dwell here. Outer Darkness is most closely comparable to the EV description of Hell (wailing, gnashing of teeth, etc.).
--Telestial Kingdom: Murderers, rapists, serious sinners will dwell here. However, since God is merciful, the Telestial Kingdom is still a kingdom of glory. Joseph Smith once commented that if one were to see the Telestial Kingdom, they would commit suicide to go there. (No, I don't have a citing or documentation for this quote. For all I know, it could be a Mormon urban legend, but this is something I heard often growing up.).
The Terrestrial Kingdom, or "middle kingdom", is where most people will end up. This is the kingdom where people will dwell who have committed minor sins, etc. I was always taught that there would be more Mormons in this kingdom than any other. We as members have more responsibility because we were taught the gospel here. We are held accountable at a greater level than non-members. Non Church members will be taught the gospel in the next life, and if they accept it, will be exalted in the Celestial Kingdom. I never really thought this was fair. I thought, "Gee, why couldn't I just be a non-member? Then I could be given a little more slack, and still accept the gospel in the next life. Doesn't seem fair!"
The Celestial Kingdom is where everyone really wants to be, but you have to be almost perfect to get there. This is the only place where you can dwell with your family, and with God.
For me, and I think for most Mormons I knew growing up, the Terrestrial Kingdom was the real Hell. Living eternity knowing that you were given the gospel in this life, and you just couldn't quite measure up. You spend eternity not being able to be with your family, and be a servant to those who are deserving of a "far greater glory".
No wonder so many Mormons are depressed, and dealing with perfection anxiety. *sigh*
I would like to take the discussion in a slightly different direction than Scratch's thread, and focus on this middle kingdom aspect of hell.
Did anyone else who grew up in the Church fear this middle kingdom as much as I did? There were many times when I just felt like "why bother?" I felt like I was going through the motions for nothing. I was always going to screw up, so more than likely, I wasn't going to be with my family, anyway, and would end up in that dreaded "middle ground".
Is this just the weird perfectionist in me coming out from being a musician and feeling like everything has to be perfect, or did others feel this way, too?