Burpees are awful.  If you've done only one, you are already aware of this.  They are used as a penalty for not completing an obstacle at some of the fitness races.  How bad must they be if they are used as a punishment at an already grueling event?  Quite simply because they are a great tool for making improvements to your health and physical abilities.  If you look at the motion and efforts required it's actually pretty easy to answer the question as to why we should do burpees as a regular part of our workouts. 

Steps 1 to 2:  You use your core, legs, and upper body.

Steps 2 to 3:  Relying on your upper body to stabilize the rest of your body and tighten the core to thrust your legs back.

Steps 3 to 4:  Again use the core and upper body to bring your legs forward.

Steps 4 to 5:  Lastly you utilize your legs to thrust yourself upwards. Take a look at the muscle groups used below: From this diagram, you can see that all the muscles used are of the utmost importance to the hunter.  Plus, when using multiple muscle groups during the same exercise you'll be burning some serious calories.  Just by the dynamic nature of a burpee, you're getting a great anaerobic workout.

There are many different iterations of burpees out there to consider.  I don't get into too many variations, but depending on the exercises I do accompanying my burpees, I like to add a push-up during stage 3.  I've also seen where adding a weight vest can really take this workout to the next level if you're so inclined.  The best part about burpees is you can do them anywhere and without the aid of any weights or equipment. Try them for a week or two and see the improvements they make.  I bet after that they find a place in your off-season training.  I know they did in mine!