gogold,
In my opinion it's comes down to how valuable is my time. By this I mean this: If it takes me days on end to harvest the gold from a source, and the yield of gold is minimal compared to my efforts, then I have wasted time that is better spent elsewhere. There are parts of the board pictured that are obviously worth the effort of recovering (CPU, Memory sticks, cards, and pin headers).
The traces on the board pictured are all copper. The coating Mayhem mentioned and the solder mask (the golden colored laminent you see on the bottom of the board) makes the board difficult and time consuming to process, for very little return (some copper and little, if any, gold).
The second thing to consider is the chemical cost. Do you want to use your precious nitric dissolving the mass quantities of tin, copper, and nickel which is the bulk of the metals on the board and slots? Or do you want to use this nitric for a controlled 'attack' on the higher yielding parts previously listed?
The point I'm trying to make is that if you plan your processing time properly you can do your harvesting work while your higher grade gold plated parts are soaking or dissolving. This is why I like the slower indirect (nondissolving- gold doesn't dissolve) methods of recovery. I can harvest my boards of the higher yield scrap, put this into the appropriate bath and them continue my harvesting efforts while the gold is being processed. This way I get the most for the least effort.
A few added bonuses to slower methods are:
1) Cheap readily available chemicals.
2) Low fumes
3) Little to no babysitting of the reaction.
4) Your gold always remains visible during the recovery process. This is a big plus for newbies who frequently are 'losing' their gold once it 'dissapears' into a liquid solution. If you can see the gold, you know right where it is at all times and it's much harder to 'lose'.
There are several other threads on the subject, search for 'PCB' or 'board' and you'll find them.
Steve