Per the Total Rewards mag found in
HET property rooms:

Go to www.trmarketplace.com/2x
to earn double reward credits on
your FIRST PURCHASE -- thru
29 Feb, 2012. For general purchase
conditions see--
www.totalrewards.com/marketplace/terms

As far as I can tell this is for ANY FIRST
purchase and does NOT involve using
a TR credit card. So if you're making a
large purchase and want some extra
TR credits for "free" it may be a good
way to pad your account!
(PS -- does not apply/add to your
tier score)