Here's my story: I started running ~3.5 years ago, and it has become something I love. I've trained for a couple of distance races, but for the most part I'm happy as a 20-25 mi/week girl. I don't push it particularly hard, I just enjoy getting out and feeling the ground under my feet.
I've been eating paleo for two months and so far I really, really like the way it makes me feel. I didn't realize how much the blood sugar roller coaster affected me until I got off of it. I haven't been purposefully low-carb, but in my efforts to stay low-glycemic-index, I haven't been loading up on the fruit and sweet potatoes. Unfortunately, I've had to drop running, because my energy level was just. Not. There. I read "Paleo Diet for Athletes" when I was first starting out, but I assumed it wasn't relevant to me because I'm looking to jog around my neighborhood, not complete an Ironman. But now I'm reconsidering.
I'm working on adding sweet potatoes and fruit back in; and I'm also really curious what other runners' (or cyclists', or swimmers') experiences have been on paleo. Did you need time to adapt to the diet before your performance was normal again? Do you purposefully add carbs, or do your cravings guide you appropriately?
(Please, no admonitions about "chronic cardio." Even if I didn't believe that humans are born to run, it's an activity that I love and that makes me happy.)