Arguably, everyone who spends time on their feet can benefit from Five Fingers. They may initially complain about the lack of padding, but once their foot muscles begin to build up, they'll find minimalist shoes not as uncomfortable. Many people who spend time standing most of the day (like hairdressers) also stand on cushioned mats, so their feet won't get that sore initially even in Five Fingers (but they'll still be able to better feel the ground beneath their shoes). A lot of back pain issues can be resolved by properly standing, which most "traditional" shoes don't let you do, because they leave your feet squeezed and heel raised.
Do your feet change after wearing Five Fingers for awhile? Certainly, but not to the point where you can't wear "normal" shoes again. You'll quickly find, though, that having to wear normal shoes isn't as comfortable as Five Fingers, so you'll be less inclined to /want/ to wear other shoes after wearing Five Fingers for awhile.
We wear Five Fingers almost exclusively when not at work (unless we're going out to a fine restaurant or something), but have to wear dress shoes at work. We hate our expensive business shoes now, but there's no physical reason we can't go back and forth (other than the fact that it's "better" to wear the Five Fingers from a biomechanical perspective).