Provided the subject is well lit and contrasty then the auto focus is fast and (generally) accurate. If it's dull or hazy forget it. I often switch my F90X to manual focus to stop it hunting back and forth I think this is a generic AF problem, not one confined to the F90X.
Otherwise, yes it's a good camera, quite chunky with the battery pack, but ergonomically sound. Works well with the SB26 flash unit too. At the sort of prices being asked nowadays it would be a bargain not to be missed!
But I still prefer my F3....
Richard