I'd consider doing tough mudder but I have a solid training schedule for Sydney Marathon.....also I am a bit of a noob w.r.t. climbing things and jumping off stuff. Finally it looks dangerous, I worry about marathoning-ending injury.
If you do it, book your starting time for as early as possible. I did it last year 8am start and we had a clear run to go through at our own pace. My mate went midday on the Sunday when the track was pretty shagged and it took them 4 hours to finish. Most of their time was standing around covered in mud in the cold waiting for each obstacle.