How good is Vista about automatically running installers as administrator?

I've read that there's "heuristic detection" code in Vista's UAC to
automagically sense installers (by more than just file name) and issue a
"Run as administrator" behind the scenes so that you don't have to do it
yourself -- but how good is it?

What I'm hoping to avoid are the cases where that doesn't happen and the
install bombs halfway through because of a rights issue, or worse, the
install does appear to complete successfully but really didn't.

Should I just "Run as administrator" on everything I install for good
measure?

I should note that I have "User Account Control: Behavior of the elevation
prompt for administrators in Admin Approval Mode" on "Elevate without
prompting" (I just can't take the prompts all the time, but at least UAC is
still enabled), so what's elevated and what isn't is a bit of a mystery.