ff programs
 

Does anybody know what people prefer the most
about a ff program? Is it the free tickets, is it the upgrade or is it something completely different? Do you know if there's
a research about this topic?

I have seen quite a bit of research on this topic by both Randy Peterson and Co as well as airlines themselves. Unfortunately, I can't remember where exactly I saw these articles but if you dig I'm sure you can find them. Generally speaking, these surveys have found that most frequent fliers consider UPGRADES to be the top perk of frequent flier programs more than any other benefit.

When travelling on business I value Guaranteed Availability (ie. there are no seats left, but we will kick somone off the flight for you).

When travelling for pleasure (as if) it is upgrades.
MF