Coming over from 7-series BMWs, a Subaru and a Passat into a Discovery 2 was a bit of a leap from a wrenching standpoint. Everything seems to have tolerances that you're not used to in German or Japanese cars, where things attach to other things in one way only. But you get used to it. There are some frankly idiotic solutions at times (the oil filter location on the TD5 comes to mind...), but then again life wasn't always roses with ze Germans either.
From a reliability point of view, I can only speak from personal experience. The stuff that has given me the most grief the past 46,000 km have been rusty pipes of various descriptions. One brake line (which has to be routed manually along the bottom since the originals go partly above the frame but under the chassis), the cooler line for the automatic transmission (goes to the front), an ACE pipe and a high-pressure power steering pipe.
In addition to that, I fixed one of the traditional ABS faults by replacing the valves attached to the modulator. 30€ part and three screws once you figured out the problem. The ABS has failed on every single one of my cars at some point or another I believe, so I wouldn't say the D2's ABS is particularly prone to fail. An ACE pipe had rusted through, and the rest of the pipes were probably not far behind so rather than to keep throwing money at it I decided to simply bypass the ACE pump (there are kits available, it was 300€ including parts and about 1,5h of labor at a specialist, the most expensive part being the roller that replaces the pump). Both the transmission line and the power steering were stupidly expensive to repair at a specialist.
Sure, there are electronic gremlins as well. When it rains, the body control unit might get moisture and start throwing up warning lights.
Alright, all of this being said... it's a great truck. Every time I drive it I absolutely love it. More than capable enough off road, far more capable than what I'm comfortable putting it through. Without the ACE it gets quite a bit more lumbering to drive, with ACE it's a dream. It's a future classic, if only because they are about to go extinct as more and more of them develop problems that are uneconomical to fix.
My advice is to find the best and newest one you can, with a solid service history, and to specifically spend time crawling around underneath and inside with a flashlight, a rag and some oil cleaner spray, poking and prodding and taking a good hard look at what the various pipes and joints look like. If it looks like a power steering pipe has been MacGyvered together then my bet would be that some similar line is about to need some MacGyvering too.
