Your profile does not list where you come from but as an East Coast person, I find transferring to Cathay Pacific's AsiaMiles and using it on their OneWorld partners, especially British Air, is the best bang for the buck. For example, it takes 80,000 Asia Miles to get a Business Class ticket from the NY area to almost all of Europe, while the same ticket on BA costs 100,000 miles. BA charges 75,000 for Premium Economy so for an extra 5,000 miles you can go Business Class instead! In addition, using it on AA for upgrades gets you the same seat but without the AA significant surcharge.

The only caveat is that it can take up to 30 days to make the transfer, but Cathay is one of the few that will make the reservation pending transfer of points.