If you sit in close proximity to the TV, with the TV directly at controller level and face it directly, yeah, you'll probably see some glare.
If your TV isn't bright yet very shiny and freshly waxed you might actually notice it too.
I see this as a huge problem, which might blow up in Sony's face.
Well considering the light is there so it can be tracked by a camera thats below or above your tv, I would assume that the light will be directed at the screen.
Also, plasma TVs are glass, and a lot of high end LCDs use a glossy screen as well, since it more cleanly allows the colours from the TVs pixels to permeate the screen with less reduction to the visual quality. These types of televisions are quite reflective, in broad daylight, they will reflect a large amount of the room that surrounds them, its a big reason why people will recommend you only get a plasma tv if you have a nice dark basement.
Now if you are playing something bright and colourful the reflection of the light in the dualshock4 will be either hard to see, or just hard to notice, and thats fine, it will only be a minor hindrance at those times. But if you are playing something dark, like say a horror game, or even something like the darker sections of The Last of Us, then the light will be quite bright, as it will be one of the brighter things in your room, since your TV is mostly emitting black (which if you have a nice plasma is actually a lot closer to a black than most LCD TVs), in these instances it is very likely that you would notice the coloured light emitting from your controller, not just around your legs where the controller is resting, but also the reflection of the light off of the television.
I hope that explains why for some of us this will be an issue. Im glad this wont be an issue for you, since you dont seem to be someone who owns a plasma or a glossy screened LCD television, but for those of us out there with these TVs it is possible that it will become very distracting.