"and the GUI has always been in DOM0 with no networking."
I'm clearly not a Qubes user. I'm basing my statement on what articles or comments here described as relatively recent work isolating the GUI stack further from attack. If that didn't happen, I retract it. The Xen, Dom0, and driver risks she ignored and countered directly so I was sure they'd be a problem.
EDIT to add: Btw, she later did a one-side rebuttal countering various things here on her blog while censoring my rebuttal of course. One real problem she identified was my use of "military-grade:" commonly a buzzword indicating snake oil. I read lots of defense stuff back then but forgot to translate. I meant Type 1 certified by NSA for high-assurance use in military. It's a rigorous process identifying and often preventing... many issues people found in proprietary and FOSS products designed without high assurance practices. ;) So, I started saying NSA Type 1 certified from that point on to avoid confusion.
I've only used it on mid-high end systems though. You should easily be able to launch a few small VMs (each AppVM is tunable) on a dual core machine with 4 GB of RAM though.