It's a blast. Did a 5k obstacle run last march with a group of 12 outside of Houston. Our group ran as a pack and whenever we hit a new obstacle we all had to take a drink. After the 6th margarita it became pretty comical.
I did the 13 mile spartan run last year and had a blast. plan on doing it again in december. i found out there's a way to run it for free so i'll be looking into it