IMHO the reason people never give upgrading OSX a second thought is the learning curve. Apple does not change where things are for no reason. Microsoft seems to be supporting bloated IT departments with needless changes to system setting menus. Someone has to learn and then teach where they were moved.
Case in point:
My Mom (82 years old) upgrades her Mac with every OS apple comes out with and never misses a step. Her needs are quite similar to my Wifey who teaches yearbook at the local school. Both use Photoshop, excessively email, make slide shows and albums. Wifey is running XP because Vista required learning new places for the same old or slightly upgraded settings. I doubt she will change to Vista until Microsoft forces her to for the same reason. You can guess who is having a good user experience.