Just recently swapped out the drops for horns. I run them with the CX levers - when I'm riding in traffic where I am braking a lot I'm on the tops of the bars. I like the look of the TT levers, but for me it just wasn't the right area to put my levers.
I'd say I switch between the tops and the horns equally - when I have long stretches where I can just cruise I'll be on the horns, when I'm going from light to light and in traffic I'm on the flats.
I currently have a stem shifter, but want to put bar end shifters on eventually. I think that'll be my perfect set-up - CX brake levers, bar end shifters, on a bullhorn.
Here's what I commute on: