With respect to build quality - I don't think there is a step down at all between an E39 and the new X5M.. in fact, to the contrary, I think the X5M is the best built (materials notwithstanding) BMW that I've driven and/or driven in.

No squeaking/rattles/anything. 2500 miles.

With respect to build materials - that's a conscious decision by BMW to save money.. Not bad materials, just some cost cutting where most people won't notice. That is not a BMW only initiative and IMO is no reason to avoid the X5M.

Your other options are the ML63 (dated and fugly) or Porsche CTTS (dated and expensive).

__________________
Go 50i or go home