Hey,
To answer your question, yes there are long distance runners here who follow lowcarb plans.
I've done Atkins for over a year, and I have been a runner for about 15 years. I favor the longer distances, race 10K's nad half marathons regularly and just did my first marathon in June.
Carbs are really overrated among runners. Many runners eat only carbs, sacrificing protein and not eating enough fat! When I ate the typical low-fat, high carb way my performance and energy levels were not so great. After adjusting to the lower carb lifestyle, I am much stronger and fitter and a better runner. I eat very healthy, non processed foods with high nutrient values. My msucles are like rocks! Dietary fat is a great fuel, andt he amount of protein involved in a lower carb lifestyle is muscle sparing.
It is going to be hard at first to adjust to the lower carbs. If you are going to do a lower carb plan I would suggest not doing any of the induction phases which most palns start out with. If you are going to do Atkins or South Beach, you would probably want to start in their pre-maintenance phase.
I eat very low in carbs, getting my only carbs from veggies (okay, and from dark chocolate as well, but hey, why run if you can't eat any chocolate). At first I was totally ZAPPED in energy, but I eventually adjusted to the lower carbs. In my marathon training, I found I HAD to eat some carbs before my long (15+miles) runs and I would take GU during the run.
Hope that helps some!