OP, fwiw ... I ride a 'flat-bar road bike' -- it's my only bike: three-season commuting, longer weekend rides (40-60 miles routinely), and a couple of century rides over the past two+ years. I have no problems with the positioning or the available hand-positions (four: grips; out on the bar-ends; grip/bar-end corners; hands in near the stem). One does give up a fully-sustainable 'aero' position (including the drops), but that's about it; to me, that doesn't matter, to others it does. If so, drops are the way to go.

However, I wouldn't take a bike designed for drop-bars and just convert it. As a couple of others have noted, the geometry is just wrong, unless you really do want a kind of 'sit up and beg' riding position. You need at least another 2 cms or so of effective t/t length (relative to a drop-bar bike the same size). Giant, for example, does exactly this with their Rapid series (which is simply a Defy with a 2cm longer t/t).

I've attached a (crappy, I know!) pic of my Sirrus, for reference: