Hi
They are a rare beast compared to the number of diesel cars around and even the 4.8!or 5.0 models, although saying that there are about 9 on pistonheads from 25k to 40k approx, so take your time, there are nice ones and some less well maintained cars out there.
Recently when thinking about an E70 I did start looking at a diesel but doing only 2-3k miles a year and no being able to find a car that fitted my spec sheet I started to look at an X5m. Whether you do choose a petrol or a diesel, I had advice from Jason's son at BW Chiptune about retro fitting options on E70 and it's a lot harder than on the E53, so find a car with the spec you want. If you want a heated steering wheel it's easier to find a car with it on than pay about 2k for retro fitting one! So do your homework and having an E70 already you probably have an idea of what options you need and want on a car.
If you go for a BMW used approved car generally they have a better spec and lower mileage cars when you look around, and also you get a better warranty with them, but they appear to charge more for the cars in the first place. Some forum users have been disappointed with the condition of some used X5m examples when seeing them at independent garages. When looking it appears the better condition and spec'd cars generally go quite quickly in under 2 weeks when I was looking.
I have seen a few cars and enquired about a few others some of which had a basic spec and have had a test drive of one recently and it was addictive power and yet it was smooth and more refined over my E53 4.4i V8 petrol, I think the word was effortless. It definitely puts a smile on your face when driving one and a tingle down your spine from the sound and yes you don't need all that power and a diesel would suffice, but you do only live once and sometimes you just have to do what your heart says rather than your head, and if the worst happens you can sell it and get a Nissan Leaf
). I would take a test drive and see what you think as its probably not everyone's cup of tea.
Yes there is tyre noise from the run flat tyres and probably similar to your car especially if you have 20" wheels and runflats, but no worse than the 20" standard Bridgestone tyres or the 22"s with Yokohama tyres on my E53.
The fuel consumption can be a problem for some, but on test drive I saw between 13 and 25mpg depending whether accelerating and cruising which was not much different to the E53 I was driving depending whether in towns or on a run and even possibly slightly better.
It really depends on what you want from the car, the sound of them one is nicer and more purposeful than my V8 and I guess than a diesel as well. The comfort is nice, but probably similar to your existing car, for me I thought the head display I initially thought was gimmick but the further I drove on the test drive the more I appreciated it and it did remind me of the speed limits and I ended up adjusting my speed, so you can train an old dog as the saying goes.
Also it depends on how much you drive it and I guess how much you are prepared to spend on running the car not just on fuel. It's a bit like the E53 they are OK to buy and some are sub £5k, but if they go wrong they do cost a bit to repair and maintain.
Iirc I think a major service, inspection 2 at BMW is approx £880 when I enquired but a minor one inspection 1 was about £500 and an oil change about £300, but it is all condition based servicing on the cars now so some go 9k miles others 18k or more between services which is probably more expensive than the equivalent service on a diesel version.
Again another consideration is road tax as they are in the higher road tax bracket, but so was a 335i convertible BMW or an M5 and also a Range Rover sport diesel when I was looking at those 3 cars a while back all circa £500 a year, which is about £10 per week and better value than a lottery ticket.
Again I guess insurance can be an issue on whatever car let alone one of these as I believe they are group 50 so it's worth getting quotes on their cost to you in your locality and your driving record. The quotes I had were about £400 more so about double the cost of my X5 insurance, but again the cost of the X5m was at least 5 times the value of the E53, which made me wonder if I was being overcharge for that car.
For me when looking at doing the numbers the running cost weren't too bad, but then first off I am only driving
2-3k a year at the weekends, and secondly I was looking at reducing the number of cars by selling two cars an X5 and the 135i convertible and compared their combined running costs against the running costs of an X5m,
Would I buy one? the answer in a word is yes
and as my brother in law says to me when he turns up with a different sports car it is the reason why he goes to work.
Hth
Graeme