Yes, but UAC on my Win7 Ultimate x86 is tweaked to Notify me only when programs try to make changes to my computer (do not dim my desktop). UAC can be very annoying, sometimes.
i leave it on, its another security addition and may just help at some point in the future, you never know... it doesnt pop up very much on my machine for me to turn it off for nagging.
i have it completely off also i feel well protected with the security that i have and i try to be safe always
I have it on and do not recommend otherwise. You really don't want everything that runs to have full access to everything.