[MatthewPhillips]

Run an update of 60 packages, browse the internet while waiting for it to complete, find a .deb you're curious about and try to install it. You can't. Regardless of dependencies. Apt uses a global lock. That is bad UX, whether you acknowledge it or not.

[ktizo]

How often, other than when you run the first large system update, is this a real issue?

I mean, I'm all for the *.deb to automatically queue when clicked, as that would be nice, but I do not see why I would particularly want it to mess with the system while the system is being messed with.

Also, I could always virtualise if I want the functionality of having an explicit split between system and userland.