Yea, I am having the same problem. When I cradle the phone with my shoulder everyone says my voice is garbled until I grab the phone again with my hand. Very strange.
I get the same issue... If I'm laying on my back and the phone is "upside down" meaning, the mic is facing the ceiling nobody can hear me. They all say, "Hello? Are you there? I can't hear you" but I hear them fine. Second Droid, same issue..
I'm going to do some tests to find out what position the phone has to be in to have this happen. it doesn't make sense. When someone tells me they can't hear me I keep the phone in the same position held to my ear and sit up and it just starts working again. My bed does suck, but I'm gonna rule that out