Ok, The Render Preview window dosn’t seem to care what the size or “hard” value of halos is. I tried to tweak a halo with it and I couldn’t see any changes. (there should have been some changing the size from 1 to 100)
The preview window doesn’t do a lot of things correctly because it really in’t a substitute for a render. If you want better OpenGL previews then you might try one of the GLSL builds from graphicall.org. These builds won’t do you any good if you don’t have a graphics card that supports GLSL so try googling your card or check it’s manual B4 downloading the build.
Are you referring to the quick render thing at the bottom of the 3D view? I am talking about the full preview (shift+P) that uses raytracing and calculates shadows and stuff like that.