Yes, we are currently doing it. We are cruising from Hong Kong to Alaska in April/May 2013 and needed to get from north eastern Ohio. Our choice is flying to JFK, staying overnight and flying Cathay Pacific premium economy seats to Hong Kong and then flying United from Anchorage to Akron Canton. In order to do this, we needed to set up frequent flyer accounts for both myself and my wife with both airlines. The fare to JFK and the hotel will be paid with cash (better value). One night in the Renaissance Hong Kong costs 30,000 reward points booked using Marriott on-line.
This process must be started no later than 6 months before the trip. We own 4 weeks and the rewards have been collecting in my account. We had to receive a faxed form, sign it and return to authorize a transfer of rewards to my wife's account (email not allowed). United charges a large fee to transfer between frequent flier accounts and apparently Cathay Pacific does not. Learning this process has taken around a dozen phone calls to both Marriott and one to Cathay Pacific because a travel agent gave us false information on the amount of Asia miles we needed. Cathay Pacific takes 2 to 4 weeks to post miles, but is holding the last two seats hopefully long enough. The awards are wandering around in their computer system.
We are currently waiting for the four frequent flier accounts to post so we can book the flights. United's web site has a wonderful tool. You log into check flight, pick rewards and the available seats for the flight on the day are displayed.
Since travel agents can't book reward flights and hotels I have found hipmunk.com very very useful.
Will update as these pending transactions are complete.
An update on using Marriott points for Asia Miles. All of our transfers have posted except one. We talked to Asia Miles and was told to mail the missing miles form to Hong Kong. (No email available) US Mail costs $38, takes at least four days and the fastest service isn't available to a post office box. We have provided documentation from our Marriott account and a cover letter explaining the situation.
So far Asia Miles has extended the hold on the last two premium economy seats. Normally, the length of time it takes to fix problems would not be an issue, but how long should it take?
I think the cause of the missing miles is that multiple points were transferred on the same day in the same amount. A clerical mistake has caused much worry, many phone calls and now expense.
I recommend that when dealing with Asia Miles you should request mile transfers on different days. This would take several phone calls to Marriott, but may avoid this type of problem.