Very very useful for getting out of sticky situations. It will protect you against anything the enemy can throw at you. It also has some cool offensive capabilities...
Any incoming missiles that hit the shield will change allegiance and go after the enemy. You can see the red missiles in the image have turned around and are zipping off to punish the enemy.
The shield will also push back smaller ships, inflicting damage each time. Wade through a swarm of bad guys and watch the destruction ensue!
And that's the Reflect Shield. Not to shabby eh? Next time, the Micro Missile power-up.