I've got trekking/butterfly bars on my Surly too. Works great for me. I have Paul's Thumbies to shift with and some direct-pull caliper brakes. I tried various positions on the bars for the levers, eventually settling on what seems to be the standard mode that most people use (with all levers on the closest, flat part of the bars). I also put on some ergo-grips, they are really nice too.

I like all the hand positions, especially when climbing for hours in first gear going very very slowly.

I tried some slightly curved flat bars at some point; that looked really cool but made my hands hurt.

Cheers, A.