Right now, you can earn a 50% bonus on all hotel points that are converted into US Airways Dividend Miles. US Airways has a number of hotel transfer partners, including Starwood Preferred Guest, Hyatt Gold Passport, Hilton HHonors, Marriott Rewards, IHG Priority Club, and many more. However, since almost all of them involve truly abysmal conversion rates, the only one worth talking about here is Starwood Preferred Guest.
Starwood Preferred Guest offers a 1:1 conversion ratio into US Airways Dividend Miles, and even includes a 5,000 miles bonus for every 20,000 Starpoints that you transfer. Hence, taking into account both offers, every 20,000 Starpoints transferred will net you 37,500 Dividend Miles (a total bonus of 87.5% and a transfer ratio of 1:1.875). Usually, I would jump at such an opportunity... but the fact that we are dealing with Starpoints makes this a much tougher call.
Starpoints are among the most highly valued loyalty program points/miles out there, and with Starwood Preferred Guest's cash and points options, you can often redeem them for more than five cents per point! That is almost unheard of when it comes to hotel award charts. So unless you have a huge stash of Starpoints or you have a Dividend Miles redemption in mind already and don't have enough miles, I would say hold off on any transfers.
Other blogs have also discussed taking advantage of the current American Express Membership Rewards transfer bonus to Starwood Preferred Guest. Typically, the transfer ratio is 3:1. However, through March 31, 2012, you can earn a 50% bonus, so the ratio becomes 2:1. If you were to transfer 40,000 MR points into 20,000 Starpoints, and then convert that into 37,500 Dividend Miles, you would effectively be transferring MR points into Dividend Miles at a ratio of 1:0.9375.
I would highly suggest not doing this unless, again, you have more MR points than you know what to do with. Membership Rewards often runs promotions for 30-50% bonuses when transferring to Delta Skymiles or British Airways Avios (with transfer ratios at 1:1.3 to 1:1.5), which would be a much better value.
If you do decide to take advantage of this promotion, note that you must complete all points transfers by March 31, 2012. This means that the activity date of the mileage transfer as recorded by the hotel must be by March 31, 2012. Be very careful as some hotels may have a delay in generating the activity date, so it is probably a good idea to give yourself at least a few days cushion just in case. US Airways must receive the hotel partner activity date information by April 10, 2012 in order to be eligible for bonus miles consideration.
Also, the terms and conditions state that only one transfer will receive the 50% bonus during the promotion, so don't expect to do multiple transfers and get the bonus on each one! No registration is needed, and bonus miles will post 6-8 weeks after the eligible activity date.