There are some people who run Windows Vista with UAC off, ...
I resemble that remark.
...because they are annoyed by the constant prompting, and are not afraid of rogue programs making changes to the system without their permission.
I can't speak for everyone like me, but what I'm not afraid of is known
programs making the sorts of changes to the system that they were designed to make and that I expect them to make. I practice safe computing and after more than twenty-five years of dial-up BBS use and operation and internet use I've gotten pretty good at it.
If Microsoft had seen fit in Vista or Win7 to make UAC work like the ZoneAlarm firewall, then everyone could leave the darn thing on all the time.
ZoneAlarm asks you, once, how you want to handle a particular action by a particular program. The choices are to block it always, allow it always, or ask always. After that, it only bugs you again when that program tries to do that action if you told it to ask. Otherwise it never bothers you again about it. It's so elegantly simple. Why couldn't Microsoft do something similarly useful instead of perpetuating what you correctly refer to as a blunt instrument, even when they had a chance to fix it in Windows 7?
If you are not one of those people, you should definitely not leave UAC off.