I've recently come back to Qubes, having last used it three years ago. I have a Dell Precision M4600, a $500 used machine that has been flawless thus far. Qubes feels snappy with 16 gig of ram and a 240 gig SSD.
When I first launched the dom0 updater I let it run for several minutes, figured it was broken, and cancelled it. A couple days later I started it, got busy doing something else, and when I returned I was surprised to *finally* have a list of updates.
This particular dialog box with it's blue bar endlessly shuffling back and forth could maybe use a percentage of progress indicator or a warning giving some sense of how long it takes. I can see where a new user would be really confused by this.