Great, but some things to be mindful of.
The first thing you need to understand when buying from this company is that this is not a regular electronics store. Everything they sell on their website is made to order, they don't have them sitting around in a warehouse ready to go. It's more like buying custom furniture than buying electronics off Amazon. Thus, the time it takes for you to get your item will be the time it takes for them to make it + delivery from their workshop in Japan.
Apart from that there's not too much to say. The cartridge reader I bought was well packed, and arrived promptly once built. They even put some Japanese sweets in the box which was a nice touch. There were no problems with payments, and you can pay with most western credit cards, and the cartridge readers are built to a high standard.