I had a set of these bars on a hybrid with a top tube that was a bit too long and they didn't work for me. Unless you mount the brake levers on the rear-facing section (where road bike levers won't quite work,) you're going to be too stretched out when you reach for them. Thus, you won't ride where the brakes are at your fingertips most of the time.

The problem is that most of the comfortable positions on moustache bars are forward of the stem clamp. The only positions that will be in your "comfort zone" are the rear-facing bits, and the very narrow section near the stem where your hands will be too close together for comfort.

The bars themselves are not the problem, putting them on a frame that fits is the key. Having said that, I felt that they weren't a good substitute for drop bars for me, I'm building a little collection of my preferred randonneur bars.

Here's the Soma moustache bar on my Specialized Crossroads, note how most of the bar is forward of the stem's clamp area: