Dear fellow iPhone users:
My story was much the same -- when I moved from the 3 to the 4, the bluetooth had frustrating dropouts, and, yes, when I called Apple, they acted like they never heard of that... Sounded like BS to me based on this forum.
But I took my iPhone to my local Apple store and they hooked it up to a diagnostic, and the guy (the "Genius"-bar guy) told me immediately "Yup, it's defective" and they gave me a new one that is working fine -- like where I can again roam around my house with the phone on a table 20 feet away.
So there. I hope and pray (for your blood-pressure's sake) that y'all can have the same happy ending to your stories.
Best. JD, Miami, FL