For what its worth, when our 02 L322 started to give trouble at around 120,000 miles we contacted Mackie in Glasgow as they have a good reputation and are used by the dealer. I only had to tell the service manager what vehicle it was and he described the symptoms to me ( namely juddering when pulling away at around 20 - 30 mph ), told me it was doing well as they usually start to go at 80-100k, not to drive as its going to get a lot worse ( just like Saint V8 describes )and book it in asap and join the queue of BMW and RR drivers with ZF boxes. He was so matter of fact about it yet precise that I realised he was right and didnt hesitate to book it in to their production line of refurbishing boxes.
A year later and now at 150,000 and no problems. The 3 year warranty is void though if we dont have the box flushed and refilled by them every 20,000 miles.