It’s absolutely wonderful for long distance endurance athletes because you no longer have to either suffer through that period where your body switches to burning fat or otherwise keep taking in carbohydrates at steady intervals. It does however, as you say, absolutely suck for weight training. I did it for about two months whilst I was doing both weight training and triathlon training and my weight training sessions were awful. I reckon I was at least 10%-20% weaker on it than previous, maybe more. Cardio was a blast though.