Mine has done 230000km, mostly trouble free driving.
There are only a few things to look out for on theses cars:
Most 4.8i V8's will have leaking valve stem seals, indicated through increased oil consumption and sometimes a smoky tailpipe at idle. This is fixable at the dealers for around R22k and should not be a dealbreaker, just negotiate the purchase price accordingly.
The gearbox will need an oil change service every 100k km, get this done asap at ZF Services in Edenvale for around R6k.
The transfer case actuator can strip its little plastic gear and will show 4x4 failure on the i-Drive. This can also be easily fixed at low cost.
Don't buy this car if you are scared of the fuel consumption. Mine averages around 15l/100km in general town/urban driving, coming down to around 11-12l/100km in long-distance driving.