One word of advice, don't do the automatic upgrade, do a full reinstall instead. After trying that for the last 5 or so releases. Always thinking that this time they fixed it. I'm not falling for that again. You'll see, as always, some reports of people saying they tried and it worked. But be careful, it's a trap!
I really don't understand why the upgrade seems to be so hit and miss between people. My current laptop has been on the same ubuntu install since (at least) 10.04. I've even upgraded to beta versions a couple of times and the only problem I've ever had was when I upgraded to the 12.10 beta and it ran out of disk space in the middle of the install. But that was recoverable.
Of course, this comment might be a trap. There's only one way to find out...
For me, I put on nonstandard software that gets removed. Sometimes software sources aren't preserved--especially if I have messed with GUI configurations.
Likewise, upgrades have always worked for me. I think I took one computer through about 5 consecutive versions without reinstalling it. Maybe it depends on hardware...
I had problems updating from 9.04 to 9.10 -> I remember it messed up my system so bad I had to reinstall it from scratch. After that, i moved to Mint for a while, and then tried Ubuntu again for 11.10 then did the update to 12.04 without any issue. I will try upgrading to 12.10 within the system again this time.
It's because the more customizations a user has done, the more likely they are have to have made a change that is incompatible with the upgrade process. It's the same for any OS. The only mitigation is to allow less customization of the files that get upgraded during an upgrade.
Huh, really? I've never had an issue and been doing the automatic upgrade for quite awhile. This is for the Server version though; I would believe it if the Desktop one is more fragile.
Server also can be hit-and-miss if you've got any irregularities in your setup...I had a rough upgrade from 10.04 to 12.04 a few weeks ago (died halfway through, system left in half-upgraded broken-but-bootable state). In the end it turned out that it was due to a no-longer-maintained package (gitosis) which I'd replaced some time ago (with gitolite) but I hadn't actually removed the gitosis package and there was some hangup about deleting the gitosis user.
In fairness, after manually resolving the problem with removing gitosis and cleaning up a couple of other half-upgraded things, the upgrade process did recover and finish successfully, but it certainly wasn't painless.
My InstallationMedia is 9.10. I had one troublesome update where it only partially completed but it was happy to complete it after a reboot (11.10). Other than that, I believe I have only had one thing function other than as I would like. In the upgrade to 12.04, it hit a point where something I had changed in /etc (turning off AppArmor for Evince, so that I could use a custom hyperlink protocol, which made it easier to work with Lilypond) caused it to stop, awaiting a decision from me on what to do with it. As a result, I got up in the morning and lo: it was only a third of the way through. Not what I had intended.
