I fly CO which only has 2 classes, so it depends on my ticket. (I also have lots & lots of miles). If an upgradable international ticket is only slightly higher than the sale prices--I'll go for using mileage. I've also lucked out using cheap fares and being upgraded at the gate due to a very full coach area. On a short overseas trip (ie. Ireland)--I'm satisfied with a good window bulkhead.