Nintendo is selling you a small white lump that plugs into the bottom of your controller and makes it do what it was demonstrated doing in 2006. It costs about twenty dollars, or you buy it bundled with Wii Sports Resort, which is what almost everyone will do.
MotionPlus adds a gyroscope, and with it the Wii Remote finally tracks rotation properly rather than inferring it from acceleration and getting it wrong. Swing a sword in the fencing game and the blade goes where your wrist went. Hold the remote still at an angle and it stays at that angle. The difference is not subtle and it is not a refinement, it is the arrival of the thing that was implied at the beginning.
Three years ago I wrote that the whole console rested on one controller demo, and that the danger was a device which demonstrates beautifully and then fails to sustain. That is more or less exactly what happened. The launch remote was good enough for a tech demo and never good enough for a game with depth, which is why the best selling software on the platform is a collection of minigames and why every third party attempt at something ambitious ended up waggling.
So the honest description of this accessory is a hardware apology, sold at retail, three years late, with a game attached to justify the price.
The defence is real and I have heard it made well. Gyroscopes were expensive in 2006 and the Wii was built to a price that let Nintendo make money on every unit sold, which is the reason the console printed money while its competitors bled. Shipping without it was a commercial decision that worked. Fine. But the marketing at launch did not say the controller approximates your movement subject to cost constraints. It showed people fencing.
What bothers me most is the timing rather than the money. An install base has spent three years learning that waggling works as well as anything else, and developers have spent three years designing around imprecision. Now the precision arrives, and it only exists for people who bought the dongle, which means nobody can build a serious game that requires it.
Resort itself is charming and completely disposable, which by now is a sentence I could write about most things on this console.