The big issue with anything "stuck" onto a screen is that it will inherently reduce some of the clarity and contrast, and quite often adds more glare. So that's something to keep in mind.
And therein lies the interest in this unique product -- it actually reduces glare. I have no doubt that it will, in some way, alter clarity of color, but the reduction of glare may offset it for a better overall viewing experience.
I often think the concern over nosy neighbors is a bit overstated. I have pretty good vision, but unless I'm pretty close to a relatively small 8x10 screen -- or even a 17" notebook screen, for that matter -- I can't really see anything important (i.e., bank account numbers, username/password logins, etc). At best, I could see some videos or photos, so don't look at photos of your significant other in lingerie, or anything of that nature, while in public. Generally speaking, these days most people won't notice or care anyway, as they're too busy typing or talking on their own digital doodad.
I was going to buy a $350 refurb'd iPad, but they sold out too quick. Oh well, maybe later.