Some of these methods have a problem. They are basically air tight, and will block air circulation. Since I hang a blanket that is porous to air over the door, and have the bathroom fan (Something I added to this old apartment, and made sure was light tight when I did.) there is air flow through the makeshift darkroom.
I do not think I would want to try and work in a darkroom with plastic over the windows and door, nor do I think weather stripping is a good idea. A sweaty, airtight, room filled with noxious fumes does not seem like a good place to work.
graywolf is right about the air circulation. I never thought about that when I used the insulating stuff, probably because the apartment I had had forced air heating and a/c, and I usually wasn't in it for more than 3-5 hours at a time. If you have such a system, might be ok for you.
for my own darkroom i nailed 3 strong tacks (unnoticeable to a landlords eye) into the door frame. hoops on the curatins can hang from it and hey presto - instant darkroom curtian!!