But that said, something could easily slip through between your checking of processes, via vectors not yet patched. Its an easy, automatic way of drastically reducing your attack surface for those people who really feel they must run with superuser rights :-/
Is it have difficult to hit Continue or Left arrow, Enter when something needs admin rights?
I suspect some people will argue its fine to run without AV, using you're same arguments of being careful and monitoring activity regularly. But you know in your hearts or hearts that that is absurd 
Of course something could slip through, but I've survived since 93.
Yes I 've been caught two or three times (literally), but I've never lost anything and it's always been an easy fix.
As for it being difficult to hit Continue, etc....no it's not.
But it is a pain in the arse!
A/V
F**k no, I'd never run without that.
The movies & music (although trojans can be hidden in them) are moderately safe, as are most of the apps.....it's the keygens that are the f**kers.