I'm in the same boat as the OP. I love this phone (iPhone 4) but I now have these two micro-lints hanging underneath the glass around the home button. I already replaced my phone once because the front and back camera was out of focus.
I'm probably going to wait until it starts bugging me more or probably later when Steve decides on fixing the antennae issue after September, if it gets worse I'm scheduling a genius appointment ASAP. I really want to know how they got in there though.