My trekking bars are great, but you're right about the shifters. I put the brakes far enough outboard that I can "fingertip" them from the sides, so they're not so much an issue while riding. Not being a speed-demon, I only use the far end of the bars when I'm grinding into a headwind, and I have a honking huge "PeeWee Herman" style mirror attached to the left far corner. (It makes a nice handstop when I use the far elbow) As for the shifters, once you get used to it, it's not much of a hassle.
That said, if I were to go all-out, I'd put roadbike brifters on the far bar and elbow, and some interrupter brakes on the near bar, or at least put some interrupter brakes on the far bar. It would look ridiculous with all the levers and cables poking out everywhere, but my hands would have brakes no matter what position I use.
EDIT: Here's a pic to show what I mean about "fingertiping" the brakes. Talk about an awkward way to hold a camera...
