I have aeros (Profile Design Split Second) on my flatbar "touring" bike. If I'm doing 15 on a flat, and drop to the bars, I usually drop down one or two cogs, and end up doing 17-17.5 for no perceived change in exertion.
I've had the bars narrow, and wide (when using my big HB bag on long rides).

Originaly got them to give me a way to get out of the headwinds. BIG help... I was resorting to riding with my elbows on the bar and holding the frame of the HB bag. They are REALLY comfy during long solo rides. Climbing while on the aeros was an experience the first time. Stayed down while doing a mile or so on about a 4%. I was sore for several days- the lower position evidently brings muscles into play that don't get used when upright. Not a problem any longer though.

Next bike will have drop bars- and aeros, with brake levers on them. I do not use them when near other bikes or traffic. Might change that philosophy once I get brake levers on them, but probably not.