I wasn't sure about the whole magnetic ring adapter concept - I imagined my 40-dollar polarizer getting knocked off and rolling down the sidewalk - but the magnet is pretty strong, and after playing around for a few minutes, I'm a fan. The magnetic adapter makes it easy to pop the polarizer off for shots without the filter, or for swapping it for a different filter if you have others that are compatible.
The filter comes well packaged in a nice reusable plastic case, with a fitted foam insert, that protects it well, which is good because Amazon just tossed it into an envelop for shipping.
The two pictures I posted here don't do the polarizer justice. The sky wasn't particularly dramatic this afternoon, but the difference with the polarizer vs. without it is noticeable - the trees are a deeper, richer shade of green, and the clouds stand out somewhat better.
The lens caps for both my Nikon lenses snap right on with the filter installed or with just the adapter ring in place.
The only concern I have with this set is the price seems kind of high to me. With Tiffen polarizers selling for about half the price of this one, and with K&F Concept selling the same filter in a standard screw-on style for 10 bucks less than this one, I don't know that the magnetic mount is that big a selling point for me. If you switch filters a lot, I guess it could make sense, but for a casual user like me, as much as I like it, it's just not worth it.