The best value, if you have the time and miles, is to use them for biz/first class on an international partner like ANA, Singapore, Swiss or Lufthansa. Even CO and UA have some decent options for long haul travel. These kinds of trips will realize you the most value per point when you consider those kinds of tickets can cost $5-$10K (in some cases each way).
Or for winter saver fares to Europe. 60k rt in envoy is a decent deal, even for US. More so if you have the master card and can book for 55k.