I played a bit with 3ds Max and I have to say, that it's the best to generate the lightmaps by yourself. I rendered two lightmaps of the exactly the same scene:
So, if this is exactly the same scene, why are the pictures looking so different? The answer: I used two different rendering engines. The first picture is rendered using "mental ray". The second is rendered with the "Scanlight Renderer". Both are included in 3ds max. I don't know which engine plasma is using to render the lightmaps, but as you can see: if you are using the right renderer you can dramatically improve your lightmaps.
Christopher
Edit: I forgot to mention: There is a slight prize for using mental ray. Depending on your scene and computer, the rendering process of the lightmap can take several minutes (up to an hour).