It's not horrible - when we did it in June, we started towards the back and ended up walking and stopping a whole lot because there were just so many people and getting through the obstacles would cause a traffic jam. If you're competitive and want to get the best time ever, then it will definitely be challenging. If you just want to have some fun, you will. There are some hills that are pretty tough but hey - you can always walk if you need to. It's a 10k, so about 6 miles with the hills isn't a piece of cake (IMHO) but it's definitely doable. Good luck!