To the OP, I have the same issue that you do, in my home, I can get the bars to drop. Driving around, sometimes the bars drop, sometimes they are rock solid. Sitting in the parking lot of my local grocery store (which is across the street from a very big cell tower) can't get it to drop at all no matter what I do, go into Target and I get nothing, barely a bar, in the back of Target, I lose reception completely, maybe because it's a big concrete building, don't know?
I was also in an apple store today and couldn't get the bars to drop on my phone or any of the demo phones. When I asked the genius about it, he told me they have "repeaters" in their store so the signal is always really strong. I don't know what a repeater is but am assuming it has something to do with boosting your reception? I'm sure someone will come along soon to educate me.