L-Button can be set to lock on with a tap or when you hold it in, and you can dis-engage it ant any time. While in targeting, you can circle strafe and jump around to dogde, which is the most useful technique in the game. Firing is done with the A Button, which is definitely unusual for first person games, but it works. Jumping is usually crap in FPS, but Metroid makes it work somehow. If you miss a jump, it's probably cause it was impossible, not because of the perspective.
Besides, you can find it for 15-20 dollars, so what is there to lose?