Most Glocks work well straight out of the box. Remember, though, that Glocks are NOT precision-fitted pistols. The factory doesn't do any fine tuning prior to shipping a new pistol.
I had minor problems with the last two Glock Model 21's I bought. Changed the noticeably soft and spongy factory springs over to standard weight (17#) Wolff Gunsprings. I, also, replaced the plastic guide rods with Wolff's steel rods. Then I ran a good 500 rounds through each of these pistols. With the exception of two of the ten magazines (Which had small plastic burrs on the inside) everything smoothed out and has, since, worked very well.
(PS: Remember to get yourself a good holster. I like Kydex. That short stroke Glock trigger takes some getting used to!)