I had coffee with Arlo Belshee today. He's done years of successful XP programming and when I say "successful," I mean increased and predicable output. In fact, the techniques he described for XP programming, he also applied to sales/marketing and got the same level of improvements. He's got an idea for the culture of a product team, including all levels of management, that makes me drool. If you get a chance to hear Arlo speak on this topic, you should do it. He's downright inspiring.
