I've got a 130lwb on an '08. mines been rock solid but then again I wouldn't expect anything else in 20k miles.
I think the big problem with any forum is that people are quick to bash a product but less quick to tell people how nothing remarkable has happened to their cars/bikes/tv's whatever.
VW have sold a million of these vans so it's only normal that some have reported problems.
'Common' problems seem to be the Dual Mass flywheel giving up the ghost but this is not just common to VW, it's a problem on most cars/vans with one, they're just not as reliable as solid ones, they are a consumable item, if an expensive one.
Most of the other problems seem to have been caught by warranty recalls so check if your intended van has had any/all of the work done. mine had 3 recalls done on it when it went in for it's 1st service, none were causing problems but were sorted anyway.
I think a lot of the problems with that big engine is the fact people who buy the big power ones tend to drive them like they stole em, often remapping them up to over 200bhp, can't be good for them??
Have a look over on http://www.vwt4forum.co.uk and http://www.brick-yard.co.uk/forum/ for a lot more info.