I've got an R reg (1997) T4 transporter. The popular 1.9 TD short wheel base version. Bought it in April, unfortunately just couldn't afford a newer one, didn't like the idea of a contract either, don't like owing people money.
They are widely renound to be ultra reliable. Unfortunately mine is higher mileage, about 170k now, although that's not much for a diesel. The keyway in the end of the crankshaft had worn so the woodruff key slipped, loosening off the cambelt and smashing valves into pistons etc. got towed to my mechanic friend's house. Having spoken to several people about this now, it seems that it is what goes wrong with the higher mileage ones that haven't been seviced properly or by someone who knows the VW engines. Mine had had a new cambelt fitted last year by a garage who didn't notice anything was wrong then... maybe they didn't know it needed a new stretch bolt
So if poss get a lower mileage one or get it with full VW service history or at the right price! Mine (like a few others now) has now had the crankshaft welded up and the head rebuilt. Luckily only cost half what a recon engine would have, but still 100s I could have done without
The other thing that went was the gear linkage bush - plastic. Cost about £1 and took me 2 hrs to fit (i'm no mechanic) but without it couldn't select a gear! Apart from that no other problems at all. Just worn out I suppose, that's what I get for spending less originally
Despite my experience I would still recommend one as I know a few people with them and they swear by them. Get a new bolt fitted to the sprocket on the crankshaft. make sure it is a STRETCH bolt as VW don't tell people it is. That means if it has ever loosened or is removed for any reason (like putting a new cam belt on) it must be REPLACED as you cannot reuse stretch bolts. In fact, it you take it all apart check the keyway at the same time. Obviously you can't do this before you buy it though...
and will need to correctly setup the timing again.
Having said all that, it always starts first time. It's fast on the motorway (90+) and very nippy around the town, brilliant turning circle, I have parrallel parked it in tiny spaces. (get the SWB version) and can get loads in the back. And there's virtually no rust on it, the bodies are very good. Just scabs where its been stone chipped/bashed by uncarful previous owners. I parked by an R reg transit the other day and the wheel arches were knackered and taped up!
I took a whole van load of hacked off plaster from my house to the tip a few weeks ago, and apart from the van being MUCH lower than usual (still had travel in the suspension) it still handled well and pulled well.
The Ex AA 2.4 TDI vans all seem to go for £5000 upwards. Lots of them around, well maintained, towbar, biggest engine they did.