I'll have a stab at adding my 2c...
Andy Walker said:
One of my questions is, is it worth it? and if so why? apart from seeing Africa's wildlife and getting a load of hassle at the borders.?
Obviously this is a question mostly up to the individual to answer

For me, the appeal is the wide open space and going to places that aren't very accessible and/or I wouldn't have the opportunity to visit very often. Seeing relatively unspoilt places and having to be mostly self-sufficient while being able to dictate your itinerary and schedule offers a lot of freedom. Roads are generally moderate to poor, so it's fun using the capabilities of your truck more than you would say driving from the UK to France.
For some people it's about the culture and seeing how other people live - I grew up in Africa, so that has less novelty for me - but your wife may think seeing different African tribes, cultures and ways of life is the greatest thing ever (she might all also think the opposite

)
Obviously Africa has its drawbacks, with officialdom and minor theft being a daily challenge.
Andy Walker said:
Would I have extra issues with this trip due to me not being from South Africa??
Nope, I guess an RSA passport might make visas easier to get in some countries (certainly the case for SADC region) but a UK passport might have its benefit for other countries. Being South African is of no benefit for such a trip other than maybe having some prior experience of Africa. Others might be able to chime in with some important points but I can't see any issues at all.
Andy Walker said:
Would I get just as much satisfaction by driving across to say China? - or elsewhere in the East? - or North to Finland?
I can't answer this one one as I haven't overlanded much and certainly nothing through Europe or to the East. I am sure there is attraction in any of these options. For sure doing a trip to the Far East of Russia, like Rob's, has major appeal. It comes down in part for your desire to rough it or to travel in relative comfort, i.e. Europe where you could stay in nice campsites with amenities or even B&Bs almost every night.
Why not start with a trip to Morocco with your wife and see how it goes? It's not too far, would provide a useful "shake-down" for your truck and overlanding preparations but is not too far from Europe or too far off the beaten track, although I am sure you could find very remote parts of Morocco to visit if you wanted more of a challenge.
Cheers,