I forgot to mention a friend who loves the M-Bars but only when flipped over. It works for him by providing a more upright position.

I switched to mustache bars almost three years ago. I put on a shorter/steeper stem, and even added a "stem raiser" to get the bars higher. In accordance with prevailing wisdom, I set the outermost parts of the bars parallel to the ground. My hands would get a tad numb, and I attributed this to the angle of the bars. I recently did a major re-do of my bike (a Surly LHT), and, among other things, I tilted the bars up a bit. Perfect. The forward reach to the curves is now less, and the angle of the outer bars conforms to the angle of my palms. Think about it: Allow your hands to hang by your sides, and, keeping your arms relaxed, swing your hands frontwards. Note that the crosswise line of your palm is not parallel to the ground. I also moved the brake levers more to the outside of the curves. So far, I am quite happy with this decision.

I've actually just resurrected my moustache bars, and I'm with you on the...I guess they're called drops? Whatever the outside part is. Parallel to the ground doesn't work for me, but with a slight downward tilt, they are much comfier.

I do like my brake levers on the inside of the curve though.

I changed to the Surly Open Bar this year and like it, not quite a mustache but close. They are very comfy and forgiving (cromoly), I have only taken them on a credit card tour sou I am unsure how they would handle a touring load. I do grocery shop with them often and they are a bit flexy at low speeds. But in the bars defense I have a CETMA 7 rail up front, which means a high and heavy load and I always shop with my dog so top speed is around 7mph.

Mounting a bar bag is as easy as a second stem.

With that setup, looks like you don't even need Road Brake levers.
but to Each their Own..