I'm roughly two for three in this department today. The three machines all had Xubuntu 11.01 and I used the update mechanism to update to 11.10 (Onomotopoetic Orangutan).
The three machines are an older dual core 32bit, a more recent, higher-powered dual core 64bit, and a netbook.
DISCLAIMER: As usual, I must state that I am not normal and furthermore not a normal linux user (whatever that is). The Unity interface can go suck eggs. It is ill-conceived and does nothing for me. The beauty of linux is that I can go and install a desktop I prefer instead. Sort of.
Aside from download time, the 64bit machine went smoothly yesterday. Not a hiccup. The 32bit machine was a much faster download and only failed installing samba. When I rebooted, it told me to go get samba to make the install complete. Good job, guys.
When my desktop came up, I was happy. This lasted up until the background reset itself to dark blue. I checked the desktop settings and saw that they were correct (NOT dark blue). I hope this is the worst thing that will happen.
The netbook was also a quick download. When it finished, it rebooted and I had completely lost use of the touchpad. Plus it set up the netbook interface. Now I seem to remember that this was the original laptop install that I put XFCE on afterwards. Unfortunately I can do little without a working touchpad. Will try a USB mouse later, when I get more time.
The install deleted tsclient, the interface for rdesktop. I have no idea why, but I reinstalled it.
Have I mentioned that I hate the Unity interface?
In addition to hating Unity, I'm not terribly fond of the Ubuntu Software Center. They went overboard to make it prettier and now it looks like it belongs on a Mac. Synaptic no longer comes with a standard install (but got retained during upgrade). I do like the NEW feature - this has been missing since the dawn of time.
I am happy to say that at this point, there is no significant change from what I've been used to with 11.04. The boot up may be a hair slower and the login screen is different. Neither of these is a game-changer.
The rest of the reviews you read will no doubt be full of descriptions of the new, colorful screens. I just don't do that stuff.
I will update you as I figure out more about the upgrade but thus far it's been just fine. Go forth and upgrade.
Edit: I also upgraded my laptop, an HP4525 quad processor unit. Smooth as silk. The only ill effect thus far is that it changed the coloring on my terminal windows by itself. Odd but livable. My `hidden' setting on a menu bar doesn't work, but that's been quirky for a while.