I am a PM and MM Delta traveller, and I have a good upgrade success rate with DL. I spent much time during 2006 travelling between the U.S. and Brazil (still domiciled in the U.S.) and I am now spending a lot of time in Chile. To here someone say that it is practically impossible to get upgraded on DL is simply not true. All of my 2005,2006 and 2007 PMU (2.5 years) upgrade certificates have been used for South American travel between ATL, GRU, EZE, and SCL. I have also used my miles to upgrade, but not frequently. I travel on business, so my travel dates are limited.