I really love KLM (Flying Dutchman) miles, as long as I am Platinum with them:
* Platinum get KLM award tickets, as long as there is any seat (paid seat) available, Platinum overrules any black-out-dates and any specific limited award-seats availability
* miles for upgrades are good on any fare
* KLM offers one-way-awards for 50% miles.
* my KLM Platinum status has just been extended another year (feb-2005), without me having paid one single ticket in 2003/4 (I only took award flights in 2003 and 2004)!