I'm getting pretty awesome with shooting without a cross hair and in 3rd person.
I only use 1st person when gun playing and when using a sniper rifle so I can zoom in and snipe from far away. It's awesome and fun to be a sniper.

The joy of getting to kill people, and not know where it's from or who.
Other thing's I do in 3rd person, but it sometimes help to use 1st when building for when I want to shoot ghost bricks. but I notice how my flying and shooting is about the same when in 1st and flying a vehicle, so I"m having a hard time deciding. I really like 3rd person because I can see everything better in some spots and I can see how awesome my character looks when using a tool or weapon or when driving a cool vehicle.
I might try shooting in 3rd person for awhile, and if I suck, I'll go back to 1st person. I've kinda gotten use to 1st person view when fighting.