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In several ways, the Move is much more accurate than the Wii Motion Plus. In fact, the technology in the Move is much similar to the Motion Plus. The Motion Plus allows for tracking of the Wii remote in 3D space as opposed to it's orientation. However, It's not perfect, as you'll have to constantly calibrate it by placing it on a flat surface. It's accuracy can tend to lessen as time and usage goes by, which is why you recalibrate every so often. You can kinda see this happen in the latest game Legend of Zelda: Skyward Sword where it's cursor is mainly driven by the Motion Plus, but because of that, you're often have to recenter the cursor by pressing down on the directional pad.

The Move is more precise because it has a back-up on detecting where exactly the controller is. That's where the orb and camera comes to play. The lighted orb on the controller is tracked by the camera to accurately track where the controller is in real time. Without the orb, it acts pretty much like the Wii Motion Plus, and in some games you can see this. I can't think of a specific example, but on most games, if you happen to cover the orb, or the controller is out of view of the camera in any other way, the cursor or whatever you're doing in-game will will still react to where you move the controller thanks to the sensors inside, however, it may not be entirely accurate. As soon as the orb is back in view, the game will latch on to the orb's placement on the camera feed and correct itself and precisely follow your movement.

While there are other calibrations that go on in some games, those are generally to see where you are, how tall you are and/or how long your arms are. After those calibrations, the game will adapt to you accordingly, but as for calibrating the controller, that takes about a second and mainly consists of you pointing the controller at the camera so it can track it in 3D space.

Hope that answers your question!

It's way more accurate then Wii Motion Plus, actually. I could see the difference by playing Dead Nation: Extraction, a game release for the two platforms.