I'm testing out the Golden Absorbent Ground on a couple of wood panels (with collage underneath, of course) and it is interesting!
Lay it on thick enough and it will absorb paint nearly as readily as paper, though it still definitely has a "gesso" texture to it. If I get any more panels next time I'd like to try applying the ground with a paint roller or something... Not really digging the paintbrush textures.
The thing about being able to use watercolours on panels is that it means they are no longer protected by glass! I covered the whole thing in a layer of glaze medium. Makes it look kind of "rich" and "watery". I like it!