It seems , on the lower settings at least, to only provide an illusion of protection - still that's no worse than XP - which didn't have anything like it.
Strange M$ are refusing to acknowledge it as a flaw, perhaps not, sales is what they are after.
Perhaps reintroducing the secure desktop element would still allow the prompts to be set to a less annoying level and provide a good level of security.
Unfortunately, Norton UAC Tool - brilliant for Vista - gives a superb combination of protection and prompt levels , won't install on 7.
This is what it does :
The Norton UAC tool allows an application to run with silently-elevated privileges only in a specific context, one previously approved by the user with the "don't ask again" check box selected.
This means that there is a difference between regedit.exe launched from the start->run box, regedit.exe originating from a shortcut double-click, and regedit.exe launched from a double click on a .reg file (and the context actually changes with each .reg file), and regedit.exe launched by an application (malicious or not).
Given the contextual awareness of Norton UAC tool's automatic responses, the Norton UAC tool provides a usability improvement over Vista's default UAC prompts, while maintaining obvious security improvements in the Vista kernel (such as isolation, file/registry virtualization, and user interface privilege isolation) that are all disabled when UAC is disabled.
Sounds complicated, but it is child's play to use.