For those anticipating this release in the States: You're not missing out on much.
Anyway, Wii Play is designed for you, the consumer, to learn how to use the Wii Remote. In Japan it's named something absurd like "My First WIi". Clever title aside, Wii Play relies heavily on Miis - for example, the records you break are associated with the Mii you were playing. Your other Miis also make an appearance as spectators, conspicuous joggers and what have you. This is cute at first, but the novelty soon wears thin. Just like the rest of Wii Play.
The first minigame you'll run into is very similar to the NES classic "Duck Hunt". There's several stages for you to shoot your way through, involving such riveting tasks as shooting balloons, shooting targets, shooting discs, shooting cans and shooting alien spaceships bent on abducting your unsuspecting Miis. Just like the Xfiles. Or not. The first few times you play this minigame, it's pretty good stuff. But after a few times more, it reveals it's 'true form'; a menial task with little replay value. I only had to play it 3 times to get the Gold Medal. The second minigame that bothers to show up is Ping Pong. But not conventional ping pong. No, you just control the hand moving the paddle around. Your goal: hit the ball back 100 times. I managed 77. Then I fell asleep.
The third minigame you'll encounter is called "Find Mii". Whoever came up with these names should be added to the "Pun-Maker's Hall of Fame" and then shot. This involves an even more riveting task of identifying the same Mii in a crowd. Something like 10 stages, all boring, all involving similar mechanics, just skip this one. I touched it once and haven't played it since.
The fourth minigame is about as menial as it gets. It involves learning the tilt controls for the Wii Remote. Bubbles fall from the top of the screen, and you tilt your Mii to match the Mii silhouette in said bubble. The game tries to mix it up a bit by having you change poses, but that makes the game plain annoying. Skip this one.
Next game: Laser Hockey. I like this one. You control a Retro Paddle Man, who's dog was killed by the evil other Retro Paddle Man. Your goal is to hit a puck into the goals of your opponent. Just like air hockey! The change here is not mechanical, but graphically. This game looks aesthetically pleasing, with everything neon. It's like LA. Sort of.
Snooker follows after. While it can't top Laser Hockey, it is a pretty good number. This shows off the Wii's ability to utilize 3 dimensional movements. Hit the target ball, get all the balls in the pocket, you know the deal.
Then; Yay! Fishing! Oh wait, no. It's boring. You'd be better off playing the Zelda incarnation of fishing. Again, this minigame shows off the Wii's 3D movement capabillties. Somehow they made fishing boring though. Like how Rapalla completely sucked the fun and appeal out of fishing, Wii Play does the same thing. This one is decent to play in multiplayer though.
This 8th minigame is my favourite. It involves wielding the Wiimote as if it was a steering wheel, but instead of steering a normal vehicle, you control a patchwork cow, attempting to knock down as many scarecrows as humanely possible, all whilst trying to jump over obstacles. The Wiimote is tilted forward to accelerate, and rotated side-to-side to steer. A quick push upwards will make your bovine crusader jump. This one is a blast for multiplayer, and singleplayer isn't too bad either.
The 9th minigame is also pretty good. Named "Tanks!" (oh god), it involves controlling a little tank and maneuvering it around a super deformed battlefield. Pressing B will fire your ever-trusty missiles, which can be bounced off walls to add to the strategy. Pressing A drops a mine. Your tank is controlled using the directional pad on the Wiimote, but alternatively the nunchuck can be used to steer, which I recommend. Overall, Wii Play is a mixed bag. Most of the games it throws at you are menial, repetitive and ultimately boring. However, some standout and rise above the others, but they aren't enough to save the game from being mediocre. However, seeing as this is only $10 extra on top of a Wiimote, it's worth the extra cash just for these standout minigames.