Not just bar-end levers, but the inside-the-bar thumbshifter mounting that Riv likes to do is made easier with a low-normal RD... you don't have to swap the levers to get them to move the same, (and intuitively correct,) way.
Which is, I think, why GP likes 'em so much that he went on a derailleur-making mission. One hopes that it this idea works out better than his last "innovation"... the Speedblend tire. (That one almost destroyed the company.)
Fortunately, Will seems to be a much better runner-of-businesses than Grant seemed to be. (But how the hell would I know, right?)
Of their current bikes, My two favorites are the Clem Smith, Jr. for a great-looking, smartly-designed, modern-day Raleigh, and the Platypus, because it's beautiful, rides fantastic, and has the coolest head badge of all time. Plus, platypuses are cool critters... cute little poisonous **** ducks.
--Shannon