Kazman:
as a platinum I almost always get a room on the concierge floors. The only difference between these floors and the regular ones seem to be the bathrobes.
However, I have never gotten upgraded to a suite unless I specifically raised the issue with the front desk.
One positive is that even if not on the concierge floor, I always get access to the lounge - where as at hilton, the policy seems to be that if you are not on a lounge floor, you do not get access to the lounge. Also, if the concierge lounge is closed for any reason, a plat member can get free breakfast at the restaurant in the hotel (the front desk people sometimes forget to give you the coupon for this)