Glock seems to think they have it squared away. I'm not hearing of any problems lately. Any new addition to any pistol -- light mounted to dust cover, new type of recoil spring system, etc. -- can synergistically alter the way the mechanism works. It creates, essentially, a new and different pistol that has to be tested for reliability all over again.
You might want to go up to the GATE Glock Pistol section and ask JR what his opinion is on the matter. He spends more time inside Glocks than I do.