I've just upgraded from Ubuntu 10.04 to 11.04. It went well. Here are my upgrade notes:
The machine is a (now aging) Dell Inspiron 9400. I've had this machine a while. When I was thinking of upgrading it a while ago I new the replacement would come with Vista and I'd heard nothing good about that, so I switched to Linux, Ubuntu 8.04 to be precise. It ran 7x faster, really.
Just a little of that might have been that I used a new disk drive that might be faster. A decent chunk was that there is no need to virus check every file I save to disk. And everything pretty much worked. Some small tussles with the second monitor I use but nothing major. Harder things like Bluetooth connections etc work out of the box with no messing about.
So this is the second upgrade I've done to a Linux box, and the third Linux system I've had running on it. I need to note that the way I do it is start with a clean disk and do a complete install, not an in-place upgrade. I use the upgrade exercise as an excuse to clear out the rubbish that builds up. You can do an in place upgrade if you want.
There is just one thing I'm not sure I like. They've revised the Gnome UI and made it quite a bit different. I can probably get used to it, but I can also set the user option to Classic (it's on the login screen) and it looks like the old one. This might not be available in future versions though, so I'll probably have to get used to the new one eventually.
The biggest thing I have to do, then, is reinstall the old software. Most of this comes from the distros making it trivial, but I do have to walk my old data over too.
Oracle: Oracle has a deb file that I can download and install. But after the install I'm not done. I need to run this: sudo /etc/init.d/oracle-xe configure
That asks me for a new port number (default 8080 I use for other stuff). Once that is done it runs fine.
FireFox: I need my bookmarks. I can export them to an HTML file on the old system and import into the new.
Thunderbird: Just copy the files from ~/.thunderbird in the old system to the new (actually that applies to a few other things, but I'm selective, these things are sometimes used as caches and I'm trying to clean up here.
Eclipse: Just copied the whole directory over to the same place on the new drive. I keep mine in /opt/eclipse36 (ie 3.6 ie Helios). BTW do not do this from a Windows system. There are o/s executable files in the Eclipse directory tree. A lot of stuff will work but some of it won't.
Java: I need to have both Sun Java 6 and Sun Java 5. 6 comes out of the distros just fine. For 5 I just copied the old directory over (to /usr/lib/jvm, ie next to java6)
I had a little trouble getting my local svn permissions right but that is all described here.
I notice there's one improvement over 10.04. Previously if I shut the lid it either wouldn't suspend or it would suspend but not want to come back up. Under 11.04 the suspend seems to work.
I haven't missed suspend much because the system boots so fast shutting down and restarting is no bother. But it's nice to see it there.
The one thing left that doesn't quite work in 10.04 is scanning with OCR. There are OCR programs for Linux but after I read the docs I decided they weren't ready, too hard to use. So I went to Windows for OCR. It doesn't come up much, and someone will tidy the OCR up eventually. Possibly they already have, ie haven't tried that out. It won't be o/s sensitive, though, so I don't expect 11.04 to make any difference there.
There is one other thing. IE doesn't work on Linux, of course. I have three internal work sites that don't like FF. I've not had problems on public sites though, so you probably don't care. My work around is to use Chrome which works okay. The screens look a bit funny but they do work.
But overall, this is working very well indeed. Installs in Linux have got almost boring these days, but since most people still run Windows (for some reason) I get geek points when my colleagues notice my Linux system.