Well it has gone now. And left me with mixed feelings.
Background : After testing all the possible A8 replacements, specifically trying diesel models I came to the conclusion that diesels are still not refined enough for luxury barges and are too expensive compared to their petrol counterparts. So I ended up with the 750i
Initial reaction: Brilliant! I loved the smooth power delivery, the refinement, the ride, the gearbox, tha handling. All were in a league above the A8. It was also more practical than the XJR. Didn't like the quality of the interior. Ergonomics were appalling with hidden switches, too many stalks, lots of rattles and felt cheap compared to both Audi and Jag. Fuel consumption display was scary, but more accurate than the Audi.
But then it all started going wrong. Random error messages started appearing and disappearing, relating to different electrical systems, the gearbox sump cracked, then the gearbox went into limp home mode. Thankfully wasn't a gearbox issue but linked to those dodgy electrics and fixed with an (expensive) new alternator and battery.
So my faith in the car was a bit shaken.
Then over time it seemed to feel rougher in all respects. The ride didn't feel quite as smooth, the engine felt a little lumpier. Then the engine became very lumpy as a coupe of coil packs gave up... Replaced those and all was well, although possibly still not as smooth as I remember. No actual faults displayed though. I swear the level of wind noise increased as well. No actual clear problems as such, just felt like it had aged and was getting worn out.
And the steering started to annoy me as well. It artificially weights up with faster corning. Doesn't feel pleasant at all. Not a good feature.
So in the end, frankly I was glad to see the back of it. It just felt like a ticking financial time bomb in the end, the contrast with the A8 was stark. That car felt like it would go on forever.
I would now hesitate to put my own money into a BMW. Great cars, but I get the impression that they are like old British car manufacturers. Full of great technology and ideas but poorly implemented with respect to detail and longevity. I would expect to have to give one a bit more TLC than normal, which is fine for something special like an M3 or M5, but just annoying otherwise.
How they compared:
easily the fastest, but too much power for the chassis setup. Best ride, best interior. Least space, least useful shape boot.
most reliable, very very dull though. Not very refined, road noise, engine noise. No wind noise though (double glazed).
Most refined at first.. (although non-superchargerd XJR would beat it without the whine)
Most interior space. Best stereo. Cheapest feeling
Which one would I choose now? Without any doubt at all the Jag. It just feels special in a way that the others cannot match. And the experience of my brothers XJ6 along with my XJR suggests that reliability isn't an issue.
Maybe I was just unlucky with the BMW, maybe it was due to being the first non-development 750i made. But considering we had two Lotuses and a TVR that were far less hassle it has been the worst car we have had (not counting the MGB)
Impreza WRX STi Spec-C V-Limited Toshi Arai Edition/ GTR/ Panda 100HP Pandamonium/ 316d