Generally when you get a supercharger put on by someone who's done it many times, they give you a warranty and you can be reasonably certain that it's not going to break down on your way back home.
One thing I would suggest that you look into is the difference between a roots/twin-screw type and a centrifugal supercharger to determine what you want. They have different properties and they work in different ways. The differences are rather significant in low-mid range horsepower/torque. It comes down to do you want a ton of low-end torque/hp or do you want a positively SCREAMING top end with not much gain at low-rpm. Each has their advantages, as well as disadvantages.
Other than that, as long as you have a proper tune, a supercharged engine will be as reliable as a naturally aspirated engine as long as you take care of it.