It's only really ever gone wrong once, last year on the way to Le-Mans, she got hot whilst in traffic, the wiring loom for the injectors was damaged on the very hot water hose, took me a while to find the fault, but no subsequent damage.
The car is not extremely quick from take off compared to a lot of todays hot hatches and sports cars, but the acceleration from 80mph is outstanding, even still pulling at 140mph there is still some steam left, enough to get to get to 160. she is really comfortable, the seats, although old still grip you in place. The wide 235 tyres provide loads of traction, the autobox lets it down a bit, these would be great with a manual box. Unfortunatley she is not coming out of the garage this year, saving for a house, and returning 16mpg shes not the most economical car!! Hopefully a restoration to take shape next year, and she'll be back with a few performance enhancements from AJ6 engineering, and a gleaming respray, along with re-trimmed interior. A cheap car to buy, never really gone wrong, a great weekend car. Thsi car will outpace Audi TT's Lotus Elises, faster top speed than a Boxter!!
I bought my 6 litre xjr-s six months ago and would agree with this review of the car.
For the money there is not much that can touch it as an overall package. Seeing DB7s and XK8s reinforces this point. They both have about the same horsepower (or less) and are both derived from the xjs chassis.
I sympathise with your point on the three-speed auto. I often turn out of an intersection and floor it and cannot help, but wonder where all those ponies are. When you reach 60 mph though it is impressive.
Other downsides are the appalling turning circle, which, combined with a long bonnet, makes turning out of poor visibility country lanes exciting!
MPG is not as bad as it could be, but at over a quid per litre for super the pumps are a wince inducing experience.
Overall, I think the xjr-s has never looked better, and it is a rare, comfortable and quick beast.