Like most Ubuntu updates, version 11.10 isn't a huge overhaul; rather, it improves on the big changes made in 11.04, by cleaning up the Dash, overhauling the Ubuntu Software Center, and bringing in some new default software. Here's a look at the biggest changes in the newly released beta.
Ubuntu 11.04 ushered in some grand changes to the default Ubuntu desktop, most notably the new Unity interface. 11.10 refines some of Unity's rougher edges, while adding in a few new convenience features as well. We won't go through every little change here (as there are a lot of small ones), but here are some of the bigger ones you'll notice off the bat, and (mostly) be thankful for.
The Dash, Simplified
The Dash, introduced in Ubuntu 11.04, is a nice little launcher that gives you quick access to your applications and files through a quick search. It had a few little clunks, though, that made it annoying to use in 11.04. Now, the Dash only has one button, at the top of your dock, that opens the entire Dash -- no more separate launchers for Unity Places. Instead, searching files and applications are "tabs" within the Dash itself, called "lenses", and they've added a new music lens so you can quickly start up your tunes from the Dash. In addition, the Dash has its own window controls, so you can easily maximise it if you want. It's also slightly transparent, and colours itself according to your background wallpaper, which is a nice touch.
The Ubuntu Software Center Gets an Overhaul
The new Software Center looks fantastic, and is much faster than it was before. It actually looks remarkably like the Mac App Store (I guess we shouldn't be surprised), but it's easy to browse, easy to install apps, and actually something I could see myself using now. There are still some rough edges, but overall it's a great update -- you can just tell which parts didn't get as much attention as others (browsing from the front page is great, but as soon as you enter a category, it gets a little overly plain).
Along with this overhaul is the surprising change that Synaptic is no longer included with Ubuntu by default. This may enrage some Linux veterans, but for what it's worth, you can easily install it from the Software centre first thing and move on with your life. It's just a somewhat shocking change when you boot up and search for Synaptic only to find nothing.
Thunderbird and Other New Default Programs
At long last, Ubuntu's included Thunderbird as the default mail client, and it integrates very nicely with the Ubuntu desktop. You can access it right from the messaging menu, get desktop notifications, and even compose new messages by right-clicking on its dock icon. It isn't all-encompassing -- for example, calendar integration is still missing -- but it's a very welcome change if you prefer Thunderbird to Evolution.
Deja Dup is also now the default backup tool, which should integrate with the GNOME Control centre and Ubuntu One.
Window Controls Hidden By Default
From the "really small changes that everyone's yelling about" department: When you maximise a window, the window controls disappear along with the File, Edit and other application menus, showing only the name of the app in the menu bar. Once you hover over them in the top left hand corner of the screen, they reappear, and you can minimize, restore, or close the window, they just aren't there unless your mouse is. It seems like a weird change, especially if you didn't like it when 11.04 made the application menus disappear, but that's the way it is.
A Shiny New Alt+Tab Switcher
The new Alt+Tab switcher looks much prettier than before, and even integrates window previews if you have multiple windows open for a specific app. Other than that, it doesn't work a whole lot differently than before, but like the rest of 11.10, brings a certain polish to the OS that makes it more enjoyable to use (without, you know, going overboard like Windows' Flip 3D switcher did).
New Login Screen
GDM is no longer the default login screen for Ubuntu; instead, a new login screen called LightDM (along with a pretty snazzy theme that goes with Ubuntu) will be your default greeting when you start up. It's a bit cleaner and prettier than GDM was, so it's actually a nice change, if a little surprising at first.
Those aren't the only changes in Ubuntu 11.10, but those are some of the bigger updates you'll notice off the bat. If you want to check out the beta for yourself, head to Ubuntu's beta index to download a live CD. The final version of Oneiric Ocelot is scheduled to drop on October 13.