I had a chance to crawl into Dave's @ Guitar last month. Even though I'm more of a SUL person, I get where he's coming from. One, if you don't like bugs, it provides great protection. Two, if you're in inclement weather (like the Sierra have been all summer long), it provides important mental relief.
Let's face it: if you're gonna go SUL/UL, you have to be constantly thinking. Go a little heavier + more protection, and you can almost get into a 'whatever' zone. Of course, you're not going to tempt lightning, but worrying about location, temperature, wind, rain, splash, etc, etc, all sort of disappears to a certain degree.
I thought I had a picture of some UBs in action. Here's a picture of MYOG tarp-tent, with a group of UBs behind the rock. Dave is the guy in the red beanie. Yes, he's about the size of Brian Urlacher.