I upgraded #QubesOS a few weeks ago, reinstalling from scratch. I think there are significant performance improvements on my Librem laptop. I've been hesitant to say this because I thought it might be related to it being a newly refreshed system, or switching to uBlockOrigin. But even with browsers not running, in my previous installation I could hear what sounded like constant light hard drive activity. Not to mention a lot of fan activity, though again uBlockOrigin might account for that.
I sort of assumed I had a slow laptop, and that VMs are inherently heavy swap activity. So I thought it just came with the territory. All the same, I would suspend a lot to spare my drives. But now, totally silent, even with browsers running.
@ill_logic R4.2 got a performance upgrade, not sure if it's due to Xen or something else