The fifth gear issue was a batch of poorly machined shafts from late 2000 to mid '01.

They'd let go while driving (usually towing) but you'd still have all your other gears.
They should all be well and truly gone/repaired by now.

SWMBO thinks nothing of dropping into fifth while towing and has always done it.
Ours is still fine and I've not heard of any problems locally with the Patrol 'box, which is more than I can say for a number of 78 and 79 series 'Cruisers around here.

Off hand I can't recall the year the IC model was introduced.
FWIW it doesn't produce any more grunt (although it would be good to have, performance dies in the bum on really warm/hot days without the IC) but it was introduced (as was some electronic control of the pump) to lower NOx levels and get a few more years of sales out of the old engine,

It was our adoption of Euro III (or IV ?) diesel anti-pollution requirements that led to the demise of the TD42T.

BTW I forgot to say that I really don't like the seats much.
They look good but lack support. I actually get out of the Defender much better on a long trip and I'm 187cm and mostly legs.
It's actually my knees that cop it most in the Patrol, you sit a lot lower than the Defender (and a 79 Series) and for me my knees splay too much and they don't like it on a trip but the leg and shoulder room is much better than a Defender or 78/79 Series.

Ventilation is also poor unless you crank the fan up, (and there tends to be quite a bit of heat soak through the plenum) but the A/C is very good and the electrics seem good, our power windows have never had a problem (touch wood)

[edit]the LSD is also more robust than Toyota's version which tend to wear out very quickly.
The Nissan one is very, very good for a clutch pack LSD and lasts a very long time.

As I briefly mentioned above the semi-floating axle on the coil cabs is a potential problem compared to the 79 rear end when highly loaded, but again I'm unaware of any problems in use.
The higher payload leaf rear end ute has a much heavier duty rear diff and a full floating axles.
It makes the Sals look puny
The coiler rear diff is very strong too, it's just the axles/wheel bearings that aren't as good as Toyota or Land Rover in theory.

Also some tend to wander and wear front tyres unevenly.
A visit to a truck aligner is strongly recommended, they'll wind out a lot of camber and increase the castor with an eccentric bush for the swivel pin bearing. Well worth the $.