Excellent! The Best of the Best.
This product is indeed the best of its kind! People say "oh no, it's so complicated to put it on", blah blah blah, but it's easy. All you have to do is BE CAREFUL and TAKE YOUR TIME. Actually, once you have the position right, it literally secures itself into place, with NO air bubbles! I have a PDA screen protector/filter and I have to push it in manually, leaving bubbles all over the place, unlike the HORI protector. Once it's done and overwith, you'll be glad you did. I don't even notice it and it even makes everything amazingly clearer! Definately a great buy.

Really tricky and therefore not good!
I had many problems to get the protection sheets on my Nintendo DS and in the end I had to put one of them into the trash can. This is really disappointing because I have other protection sheets for my iPod and cell phone where something like hadn't happened.

Great.
It is quite easy to put these on provided your screen is clean, but getting the screens clean isn't easy, that's the problem. Anyway, if you got them installed properly you will not even notice they are there, which is brilliant.

Great!
The way they look, the way they are to be applied, these protectors are just great! @neurokwarg: if these protectors weren't slightly smaller than the screens, it would hardly be possible to apply them correctly. Five stars for me!

Quality protection
These are excellent screenprotectors. Although the instructions are in Japanese, it is easy to apply them by just looking at the pictures. Take your time and don't rush things (I would buy two units just in case).
When you applied them correctly you should notice a immediate visual improvement plus enhanced sensitivity and accuracy on the touchscreen.

In the end I must give it only 4 stars, it could have been a perfect 5. Why you ask? The screenprotectors are NOT the exact same same size as the DS screens as they are off by 1mm. It ain't so bad for the top screen but the bottom screen I consider to be the most important, and now the edges are unprotected. It is very unlikely your stylus will ever set foot there but dust collects and gathers like they are micro-trenches.