Do they only give up property rights to their bodies, or are they also giving up their souls?

I've been confused by this as well. As Juliebird pointed out, at one point it was implied that Michael and/or Lucifer would destroy the person and leave them a drooling mess, I think when we met Raphael. And yeah, John was possessed by Michael with apparently no repercussions other than an erased memory, soul seemingly intact.

I think John!Michael went so far as to imply the Winchesters were special and the only ones who could handle their angel essence.

ETA: ita the Eat it Twilight link needs tweaking to work.

Michael said he'd leave Dean okay. I don't think Lucifer's made a promise. Also, why would he vacate Sam's body after Sam jumped him into his box? I'd totally stay, so Sam would have to stay, even if there were a way out. And then, does it matter if Sam would go to hell or heaven?

ehab--link fixed.

I'd totally stay, so Sam would have to stay, even if there were a way out. And then, does it matter if Sam would go to hell or heaven?

What I was thinking was that if Sam's soul wasn't in his body his consciousness wouldn't be either. That his body would be just an empty shell being used by Lucifer (the "meat-puppet" effect). So theoretically his soul and personality and consciousness could be safe and whole and happy in heaven. It really wouldn't matter what would happen to the body. (Which, practically speaking, would have been left to be buried in the ground/burned in a funeral pyre at death/destroyed in some manner at death anyway.)

But possibly I'm confusing soul and consciousness and the two don't equate.

But the consciousnesses are still in the body when they're possessed by angels--it's like being chained to a comet, remember?

Demons we know can and do, in the SPN verse, inhabit and animate a dead (deserted by soul, spirit, personality) body. They can also share space with a living person, heal injury well enough to keep the body functioning until the demon vacates, at least, but observation suggests the healing effect leaves when the demon does.

Angels appear to burn away the physical, spiritual and mental elements of a host. But it seems they're able to heal almost as fast as they consume--almost being the key. The longer they inhabit, the greater attrition on the body.

The Winchesters, through John's bloodline, have physical bodies better able to physically withstand angelic containment demands, theoretically for sustained periods. Jimmy was apparently with Castiel, his personality and spirit unharmed, through careful management by Castiel. Still, his experience was "like riding a comet". I think Lucifer would have little regard for sam's spirit and no use for his personality, and would take little or no care to keep it from burning away. He would consider the vessel property, rather than a loan.

I don't know about Michael. From what we've seen I think he's as cold and arrogant as Lucifer. He might make provision to cushion his vessel's consciousness, but he would consider it a minor courtesy, and not mourn overmuch if Adam dies from his duty as vessel--he was raised from the dead, after all, by the will of heaven, and to heaven he will return, a reward for his service. What's the problem?

Angels appear to burn away the physical, spiritual and mental elements of a host.

It depends on the power of the angel, according to Castiel. So he might not have done anything purposeful to save Jimmy or Clare. And Michael promised not to do that to Dean. So it's variable.

Jimmy was apparently with Castiel, his personality and spirit unharmed, through careful management by Castiel.

The key being care. Raphael took little or no care of his vessel, leaving a drooling hulk behind. Anna's, Gabriel's, Uriel's, and the other angels we've seen extinguished while in their vessels, the vessels died as well. Michael has said he'd take care of Dean. Whether he made the same promise to Adam I don't know, or don't remember. Lucifer made no such promise. In fact, he's implied that Sam would be consumed, alhough I think he wouldn't care if Sam was conscious and present for a while, or not. I don't see him planning to relinquish the vessel back to its original occupant, whether it was damaged or not.

What I was thinking was that if Sam's soul wasn't in his body his consciousness wouldn't be either. That his body would be just an empty shell being used by Lucifer

It also occurred to me after I posted that once Sam has allowed Lucifer entry into his body he's probably going to need to have his consciousness present to carry out whatever plan they come up with to trap Lucifer in hell. So unless they have a two part plan - part A, trap Lucifer, part B, get Sam (either all of him, or at the least his soul) back out again - I have no idea how they wiggle out of this one.

edit - The biggest struggle might actually be for Sam to retain his consciousness rather than for it to be submerged by Lucifer.

Where did Lucifer state that Sam would be effed up? The only cite I can find about default vessel status is that the more powerful the angel the worse off the vessel is on extraction (Free To Be You And Me).

I am assuming that Lucifer will mess up Sam, since he's at least on Raphael's level of power. Just wondering why you think that Castiel would mess up Jimmy by default, since he's never said that's the case.

serial:

It also occurred to me after I posted that once Sam has allowed Lucifer entry into his body he's probably going to need to have his consciousness present to carry out whatever plan they come up with to trap Lucifer in hell

And Sam is asking questions about demon possession, not angel possession. I'm not sure why he thinks Meg or YED experiences count.