Bought my '08 xi MT (I know most of you are talking about AT) used back in march and was still under warrranty. Right away I started to notice a loud knocking sound whenever I was stopping while turnig (like pulling in to a parking spot), or accelerating right in to a turn. Took it in under warrantly and had the whlole TC replaced. Would've cost upwards of 2k at the stealership.
I personally consider these situations bad luck. Most people post about bad experiences and horror stories, but if you look at the grand scheme, the mass majority usually doesnt have all if not any of the issues you read on here. Just some unlucky few, or those who dont perform preventive maintenance on their car.
Just my opinion....