Pros: That's the japanese version of wii motion plus. Everything original, including product, box and manual (in japanese language). But don't worry because it is compatible and works with all Wii Remote Controllers - my version of Wii is American and it is working well.
Also, it comes with an advantageous and important additional silicone sleeve.

Cons: I don't know how to get the full advantage of this product. In my opinion I am playing same way games I've already have with or without wii motion plus. Maybe for specific games it can improve performance.
Manual in Japanese (Chinese ?) language. You should follow images. But this is not an important cons. because it´s only plug and use.

Other Thoughts: I would like to understand how to have more accurately capture complex motion. That's not a problem of this product but I can't see so many improves playing games.

Bottomline: Probably I don't have specific games that can be improved using Wii Motion Plus.

Pros: Definitely genuine. I bought one locally, which looked genuine but had detection problems in Grad Slam and caused jitter in Virtua Tennis. Also, in Sports Resort, the local one would take ages to 'calibrate', sometimes not calibrating at all, with the remote icon moving even the the remote was kept still on a table. No such issues with the one I bought here. I opened up both of the units, and the DX one has the Invensense chip inside, while the local one didn't. Also, the circuit board looks identical to the one found on the net, while the one I had earlier had a very different looking board.

Cons: Could be cheaper.

Other Thoughts: This is made in China, but is the Japanese version (for sale in Japan). My Wii is NTSC/US, and this works fine (not that it would matter - hardware is all compatible).
The actual connector in the MotionPlus is a little loose, but that's the way it's supposed to be (read about it on Nintendo's site). However, the fake one I bought locally had a rattling connector, while the good one (from DX has a 'softly' loose one).

Bottomline: Could be a bit cheaper. For a couple of $$$ more, I could get a genuine one. It doesn't matter if shipping is included or not, the bottomline is what I pay for it. Even the shop where I would buy it would have paid for shipping, so that shouldn't be the deal-breaker.

Pros: It´s the Japanese version of the Wii Motion Plus. I have acquired 2 of this, and both worked well, just plug and use.
It´s a fantastic upgrade for who that wants to increase their experience with Wii. Comes with a silicon cape.

Cons: None, at moment.

Other Thoughts: Comes with japanese instructions manual, but it´s only plug and use... Who cares on reading so easy of use device?

Bottomline: Buy it if this model is more cheap than in your country. At least here in Brazil, there are at least half-priced than those that are available on any place.

Pros: Like all other buyers said - this is the real, genuine extension to the Wii remote. Actually, this is exactly the way Nintendo intended to release the Wii in the first place, but for some reason released the limping version all used before the Wii Motion Plus was finaly out.

Cons: No cons at all. The extension acts perfectly. You still have to get the Sports Resort games package to get the full advantage of this product.

Other Thoughts: If you haven't bought one yet, and you have Wii - don't waste your time - buy it now.

Bottomline: A must buy for any Wii owner.