American Express Membership Rewards is offering a 50% bonus on transfers to Starwood Preferred Guest through March 31.
Normally it takes 3 Membership Rewards points to yield one Starpoint.
Under this offer it takes 2 Membership Rewards points to yield one Starpoints.
So better than usual, and in my view better than other straight-up hotel transfer options that American Express offers. But still not good or in most cases worth doing except to top off to towards a specific award with SPG. (Then, your relevant comparison is the cost to buy Starpoints.)
American Express Membership Rewards are almost always best (1) transferring to airline miles (2) during a bonus promotion (3) for low-level premium cabin award redemptions. The hotel transfer options just aren’t as good.
Alternatively, this does represent an opportunity with some devaluation to transfer points from American Express Membership Rewards to airline programs that Membership Rewards doesn’t partner with. Using this promotion, 40,000 Membership Rewards points become 20,000 Starpoints. Starwood Preferred Guest has a huge range of partners. You could transfer to American AAdvantage for instance, those 20,000 points become 25,000 miles. So 40,000 Amex points to 25,000 AAdvantage miles.
Again, not useful in most circumstances or the best use of Membership Rewards points, but strategically useful for some.