Reflections can take a great deal of time to render, due to the way light bounces around, which the program has to calculate for every bounce! A cheap way to do reflections is to use a "reflection map" loaded into the reflection channel of the material. This is a nice technique for objects which aren't going to be up close or need to show perfect reflections.

In Vue, the easiest way to do this is to:

1) Position a camera inside the object needing reflection maps.
2) Hide the object from the renderer
3) Render out a normal or panoramic image from the object close to the ground. Panoramic is best since it will give full round view, when using panormaic format, render twice as wide, as high, for example, 800x400 pixel size. If the object is up in the air, a spherical render maybe needed instead.
4) you don't need huge map sizes as these are just reflections and are not for up close items.
5) then load the map in the objects reflection channel in material editor. Add some blurring if wish.
6) Un-hide object from renderer! ;)
7) Render as normal.
8) You may need to adjust the U and V offset of the reflection map for best effect, I find from tests so far U offset of 0.5 tends to be needed.

Other things to consider are using an HDR, or panoramic of the entire scene and set as default reflection map, just remember, that those won't be as good for individual items since the camera for HDR may be very different in position from the object itself or final render camera.

The over all effect is not as good as true reflections but takes a lot less time to render, if there's a lot of reflections in your scene.

Alternatively, render out a panorama of the sky and apply that as a reflection map.

EDIT 01-03-20008
Due to current processing power I don't find this too much of an issue now, though it MAYBE an idea for lake or sea surface scenes?

:)

FOUR: rendered map 800x400