"The SpaceExplorer is most effective with 3D applications. You can use it to zoom, rotate, and fly through any of the popular 3D programs – including Second Life, where it offers a more fluid experience than mouse navigation does. The catch is that there's no standard for 3D, so every application needs its own driver. It also works well for zooming around images in Photoshop or maps in Google Earth."
"The problem is the price. It's not cheap, and if you're wondering if it's worth the money, for most users the answer would have to be 'no.'"