Known issues with xorg upgrades from HWE stacks?

[Robie Basak]

I had an issue upgrading a friend's laptop yesterday. Before I
investigate further and spend time trying to figure out steps to
reproduce, has anybody else seen this behaviour?

It was installed on 12.04 with the quantal HWE stack. After upgrading to
12.10, xorg did not update, and was still on HWE packages. This
caused X to fail to boot - black screen.

Various xorg packages were on quantal hwe ~precise versions. I asked
apt-get to lose these (apt-get --purge ...- ...- etc); it suggested
installing the native quantal versions as a solution to that request,
and then everything worked.

The laptop has an nvidia graphics card. Everything is on defaults.

I've heard various user stories about graphic stack failure upon
upgrade. Is this a known thing, and could this be an underlying cause?
Is this already a known bug?

Robie