I agree with all of your points, I am running 10mm spacers all round and prefer the feel the steering it has a little more feel and weight as a result of the contact patch moving 10mm further out.
I ran 10mm front spacers on an E39M5 and it had a similar beneficial feel, I did 70k miles with this set up and the wheel bearings were fine. The delta on leverage an hence the slight reduction in wheel rate will also be very small. It also reduced understeer magrinally.
I am currently running 12mm rear spacers as there is room and I had a set spare set from an E46M3 (again I used them on the fronts) and it feels slightly worse and less balance than with 10mm all round.
I have spoken to very knowledgeable suspension guru's and they tell me that I should not be able to feel 4mm of additional track on a race car, let alone a road car. I will swap back to see if I am paranoid !
All in all 10mm all round appears to be an improvement to me anyway.