If I may chime in here, The cam/lifter problem seems to be confined to engines with cam actuated injectors, the Pumpe Duse motors (04-06/07 Golf, Jetta, New Beetle, Passat) And is similar to Ford and CAT injection systems http://en.wikipedia.org/wiki/Unit_Injector, Most of the failures seem to be related to infrequent/improper oil changes, Like Ford and CAT, VW speced a specific oil, with added chemicals to address the greater stresses on cam/lifter surfaces due to very aggressive ramp angle/cam profile needed for injector application.
As far as the older style mechanical injection pumps being failure prone, I believe this to be untrue, The Bosch VE pump and it's later computer controlled revisions have been the workhorse of the diesel market for over 30 years. Used by every major manufacturer of diesel engines(VW Mercedes, Detroit, Cat, Navistar, etc) http://en.wikipedia.org/wiki/Injection_pump Like any component longevity is determined by conditions like fuel quality, maintenance, etc.
VW TDI engines are well supported in the aftermarket, easily tunable, and with regular timing belts and maintenance are extremely reliable, the premium/resale on TDI cars still far exceeds that of Toyota hybrids, My 96 Passat is still "worth" what I paid for it 5 years ago.
The downside of VW cars can be the body systems and electronics, but with any car if you replace the engine a few times and push 300,400,500K I don't think any manufacturer's products will be in better condition. VW transverse automatics are trash BTW, The new DSG(electronic clutch manuals) show promise but are relatively new, and I haven't seen one with more than 120k yet, but time will tell. As a general rule stay away from a VW with a torque converter.
If you are looking for an A4 chassis car(98-05 Golf/Jetta) I would recommend looking for an ALH code engine with a manual transmission, and as with anything, look for maintenance, and be prepared to pay a premium for a quality car. I would suggest buying from an enthusiast.
If you are looking for more information I suggest:
http://www.tdiclub.com Lots of good information here
http://www.vwdiesel.net Mostly older IDI tuner/modification but a lot of good TDI too
http://www.vwvortex.comLots of good VW/Audi info here, but alot of douchebaggery, Especially in the MK4 forums.
I, until recent medical issues, worked as a VW/Audi tech at an independent VW/Audi only shop here in Knoxville, TN, depending on your location I would be more than happy to inspect a car for you.