The sushi assistant where I used to work would apologize to the lobsters before he plunged them into the boiling water. I doubt it made the lobsters feel any better, but it cleared his conscience.
Me, when I've had to just tear the lobsters apart without doing anything else first, I had no qualms. Am I totally heartless and cruel? I like to think not. This is not a debate to ever be settled, though, just like the others about "humane" treatment of animals.
I would think, though, and this is just a guess on my part, that hard-shell lobsters might be better to start in cold water and then bring up to boiling (if you like to do it that way for whatever reason), while soft-shells should go directly into boiling water. This has nothing to do with their death, though, but rather with their propensity to take on more water before the shell is hardened completely by cooking. Soft-shells are recently molted, and have a larger shell than the meat needs, so there is space that is already filled with water, and might take in more. My guess is that plunging them into boiling water is akin to sealing/searing them -- even though we all know that searing doesn't keep juices inside meat, it does form a sort of protective shell.