Canonical dropped support to the alternate ISO's and they are not listed in the downloads page, how can I do a CD ROM upgrade now ?
Apparently you can't. I've just burned a 12.10 DVD and booted off it to have a look, but it is not offering and upgrade option, only 'use all of the disk' 'install alongside' and 'something else'. It seems they have indeed removed the CD upgrade option.
Even holding down Space to get to the utility menu does not yield an upgrade.
I think there were some problems with the CD upgrade in past versions but I thought it was one of the better ideas I've seen regarding upgrades. Let's hope it comes back in future releases.