I use the MR mall a lot!I have channeled over $10,000 through them and have not had to contact customer service once.
Yes the points are sometimes slow to post-but mine have all shown up eventually.
Very happy with the # of points per merchant-some are double what the same merchants offer on the airline sites(which I also use when there is a promo on them-such as the upcoming NWA mall promo)I would welcome some better promos on the MR mall,but I guess it all works out.