Oh okay Awe, that's a tough one fer me since I don't give the topic much time for thought - too busy with the stuff I DO perceive to wonder about the stuff I DON'T. Yet.
Probably most UFO reports are not aliens but have mundane explanations (like all the New Mexico reports, they are awfully close to a military test range, which I think explains what people are observing that they aren't familiar with). But I am of course, open to finding out what else is out there in the universe.
The universe being as vast, infinite, no? - as it is, it is more logical to believe there are other planets full of life than it is to believe there are NOT. Like, really guys, ONLY Earth has life? But it hasn't been a passionate interest of mine to speculate on and I have no opinions one way or another.
I will only admit that I don't know, and that just because I haven't seen something doesn't mean it isn't there. My eyes could be closed, after all.