I try to use my miles towards expensive international tickets (the ones I would never, ever buy on my own). Of 11 Australia trips, 9 have been in business or first on miles. I've also done Barcelona, Athens, Auckland and Tokyo on miles in business in the summer months (for comparison, I was getting $1500 fares for Barcelona in coach and $1900 fares to Athens, so miles for business was a good investment). I would never think of using a single mile to upgrade, but reading a lot of the posts here I suspect I'm in the minority.

When my account balance gets on the high side, I do give family and close friends tickets. I flew my dad and sister to Australia a few years ago, and brought a friend along with me in business class to Barcelona for her first business class flight. I did spend miles for a Montreal ticket in coach next month (25K), but thought that was a good value compared to the $400 fare on that route from SFO.

Seems everyone has a different take on what the best value for "spending" miles is. There isn't one rule that applies to everyone.