Anyway, I found a solution I think to those nasty looking gradients.. it seems if you use RGB8 as the lightmap texture, and check "Save as BMP", then increase the lightmap size on the surface (depending on how big it is) to either 128 or 256 for the largest surface in the room it helps alot.
I know one might think checking "Save as BMP" would add a huge uncompressed image to the map, but apparently when I did this and rebuilt, the level went down 3 megs in size :P hehe I don't know why... but it doesn't seem to affect level size adversely. :)
Here's a comparison...
Before lightmap size changes (to the surface) and lighting changes in build options:

