Since you list other E70 X5s in your profile I'll stick to comments about the 2009 X5 35d engine compared to our previous 2001 X5 4.4i.

AFAIK there has only been one report of a catastrophic engine failure in an 35d. BMW is replacing his engine. It will be very interesting to see how this turns out.

We have about 2,500mi on our 35d since we took delivery in mid Aug. Most of those miles are on 2 lane country roads in the Texas Hill Country. The engine has completely met our expectations. As others have posted....

1. It pulls like a OX. We have already hauled 2 tons on several occasions. The 35d is stronger than the 4.4i at any legal speed.

2. It is a little noisier than a gas engine. The 4.4i purred and growled. The 35d clatters a bit, but in a good way

3. The 35d has a little delay from idle. This is not a big deal; but it is very noticeable in some situations. For example, when pulling away from a dead stop. But we find it far more noticeable on steep slopes at very low speeds (e.g. at the top of our driveway where we slow down on a 10% slope to give the gate more time to open). The 4.4i had enough torque at very low RPM to simply trundle on up the drive with no apparent effort. The 35d requires considerably more RPM to then slowly accelerate up this slope. Even our ranch truck (a 3.0l V6 manual) handles this slope with less engine drama.

4. It gets great mileage. On a typical 10-50mi run we see an avg of 24-25 MPG. And frequently see runs of 27-30 MPG. BUT our actual avg MPG from time of purchase is only 21.5 MPG. The 35d does not get very good mileage until it is warmed up. IOW the longer the run the better the mileage. FWIW the 'from time of purchase' MPG is based on a 'fuel log' and confirmed with the X5's own Trip Computer (which I set to zero just before I drove it off the lot at delivery).

Funf Dreisig