From LightWiki

A lot of things have been changed in the jump to LightWave v9 that stayed the same throughout earlier versions of LightWave (6.0-8.5), so there are plenty of things to take into account that you might not have expected:

• Plug-ins and fonts are now loaded automatically. You can turn off automatic plug-in loading in the Options panel, especially vital if you have your plug-ins on a network drive for use with Screamernet for instance.
• LightWave is now more demanding graphically, so you need to make sure you have current nVidia drivers or the latest Catalyst drivers from ATI ATI depending on your graphics card and you may want to look at the extra settings you can now change in Layout and Modeler for OpenGL display - you may have some tweaking to do to get optimum performance for your card.
• Speed-ups are really notable with Radiosity and in terms of anti-aliasing, but you need to know how to use them to your advantage. For instance, making sure you are using the Perspective Camera (or one of the other new cameras), set the AA passes to 1, which basically means no anti-aliasing, and set the Adaptive sampling to 0.01, which means that LightWave will keep refining the AA until it means with the threshold set in the Adaptive Sampling field. You won't notice much of a difference with just the Classic Camera since it is the standard camera from 8.5 and before and not much has been changed to it.