I have to chime in here because my boss talked me out of converting Candy to a flat bar roadie once I get a new ride. His logic is that with drop bars you still have the bar tops, and several other positions.
Being upright has nothing to do with the bars, it has to do with geometry. I can put a flat bar on a Colnago CX-1 and it's still going to be an aggressive ride. So something with a long head tube and relaxed angle will do you much more good.
As for stability there's a big move toward wider road bars ala mountain bike style. I'm considering going to a wider bar for stability because my mountain bike background makes me crave that wide bar.
Just my two cents.
"True, but if you throw your panties into the middle of the peloton, someone's likely to get hurt."