I get this issue. I work for a major fortune 500 company from home, and several times a day I dial-in for meetings. I always wear my headset that shipped with the phone. I've noticed that when I dial into a meeting with 1 other party, I get this issue (hasn't happened when there are multiple parties yet...). It doesn't make a tremendous difference on my end, but the person on the other end of the line say there is a very interruptive echo effect. On my end I can hear them cutting in and out as they talk. Unplugging and re-plugging the headphones does not help. The echo immediately goes away when not using the headphones. I had an iPhone 4 before this that never had this problem. I used headphones shipped with both my iPhone 4 and 4s. I hope Apple comes up with a resolution to this soon.
AT&T - 16 gb - Black
A Fortune 500 company employee... Good you told us cause now your case is "more valid"...
No friends or lack of self esteem?