I have no strong preference for or against. For racking the slide, I would actually prefer the "ears" like those on a VP9 over forward serrations if we are looking for a practical answer.
What is it really for? My money is on a need for "change". If Glock's had always come with them, their marketing would have offered us a smooth, clean Glock (no forward grip) to generate sales. Since they haven't historically had these, THIS is now the "new thing" to differentiate the new offering. In a few years, another (fairly trivial) "new thing" will be added, be it a color, finger grooves, thumb rests, grip texture, or something.
In short, if we don't like them, we don't have to get them (or we can not use them), but I don't think Glock was deeply contemplating true benefit as much as they were thinking of satisfying a contract or finding that "new thing" to add to generate sales (and later fill in the benefits of the new wrinkle when they write the brochures (explaining nDLC, first-ever factory colored slides, or Marksman Barrels!).
I would take mine with or without. For a full-size Glock, I would prefer without. But I it wouldn't stop me from buying a gun with them (SIG 365, etc.).