Also consider a set of triathalon bars if different hand positions are what you are after. My roadie commuter had a set already on it when I bought it used. Took a bit of getting used to, but, now I spend as much time in them as on my brake hoods.

I have heard of some folks here with mtbs or hybrids using them on flat bars. You might even consider both tribars and barends. Your handlebars will weigh as much as your frame, but, so what.