From BlenderWiki

View & Controls

These settings concern how the user interface should react to user input, such as which method of rotation should be used in 3D views. Here you can also activate three-button mouse emulation if you have a two-button mouse. MMB can then be input as AltLMB .

In particular, let’s just call out the Smooth View setting used in transitioning your 3D window from one view to another (e.g. from top view to side view). A higher value (e.g. 1000ms) smooths the transition from view to view, instead of jumping. A very nice effect found in other packages, even though more eye-candy than really useful!