Canonical's latest installment of the popular Ubuntu Linux distro is now available for download. The awkwardly named Oneiric Ocelot, as Ubuntu 11.10 is known, focuses on refining the core of Ubuntu's new Unity environment.

As with most October Ubuntu releases, 11.10 isn't a huge departure from its predecessors, rather it's about polishing what arrived in the last update. If you made the leap to the new Unity Desktop when it arrived in last Spring's Natty Narwhal, then Ubuntu 11.10 will be welcome news. This release improves on the Unity Desktop, fixing a number of annoying bugs and adding some more power to previously limited features like Unity's Dash and search tools.

Ubuntu 11.10's Unity Dash has a slightly more refined look, with some transparency effects reminiscent of Windows 7. It's not going to make Unity any more useful, but it does makes the transition into the Dash a bit less jarring. Ubuntu's designers have also rounded off the corners and edges giving the Dash a smoother, softer feel.  

Visual changes are always subjective of course, but if you found the Unity Dash of 11.04 jarring on the eyeballs you might want to have another look at it in 11.10.

Those accustomed to Unity in 11.04 may be slightly thrown to learn that the Dash button has been moved from the top panel down into the Unity launcher. It'll cause a bit of muscle memory failure for a couple of days, but once you adjust to it, the new placement looks much better and makes more sense.

Once you're actually in the Dash there are quite a few improvements that make Unity feel less like a smartphone OS that took over your laptop and more like something that might be useful one day.

The best news is that the Dash's search features have been subdivided to make it a bit easier to find what you need. It's worth noting that Ubuntu is now referring to these content subdivisions not as "Places," the term GNOME uses, but as "Lenses." So the bottom of the Dash now features four "Lenses" for Home, Applications, Files and Music. The newest of these is the music lens, which not only searches your music but also hooks into Ubuntu's default media player, Banshee, to play songs right from the Dash. It only offers the basics, but when you just want to hear a song it's faster than opening up Banshee.

The Dash's search features have also gained some new filtering tools to quickly narrow your searches. For example, instead of searching for "Internet" to find applications that connect to the web, now you can just click the "Internet" filter to get a list of applications. Similarly there are filters to refine your file searches by date, type and file size, and you can filter music searches by genre or decade. 

While the Dash's search features are still nowhere near as easy to use or powerful as what you'll find in specialty apps like GNOME-Do, this release is a huge improvement over the primitive search capabilities found in the previous version of Unity.

In fact, while it's still got plenty of curious design decisions and rough edges, Unity is clearly making progress, albeit slower than many would like. The good news is that this release is considerably faster than the sluggish version of Unity that shipped with Ubuntu 11.04.

The speed is even apparent in places where the visuals have been improved (and would presumably make for an even greater drain on your graphics card). For example the new ALT-TAB switcher now displays window previews, even for minimized windows. There's no noticeable lag with the new previews and they make for a small upgrade that both looks better and makes it easier to find what you're looking for when you switch windows.

Among the other, smaller visual changes in the Unity desktop is the new icon for the "shutdown" menu. Canonical's designers have added a small gear icon to the traditional shutdown icon in an attempt, it seems, to give you a hint that in fact the shutdown menu isn't just a shutdown menu. It manages to get the idea across, but doesn't really help the muddled menu beneath it which still can't decide exactly what it wants to be -- just a shutdown menu, or something more. 

Canonical's Software Center continues to be improved. Software Center has a new "Top Rated" view on the main page that makes use of the social rating features introduced in the last update. This time around it's also much faster thanks to the new GTK 3 backend. Of course it still lacks some of the features found in Synaptic, like the ability to install a specific version of a package. And note that, as of 11.10, Synaptic is no longer installed by default.

On the plus side the Software Center now support OneConf, which uses Ubuntu One to sync applications across your machines. Of course to use OneConf you'll need to have an Ubuntu One account set up.

As usual the Canonical developers couldn't get a new version of Ubuntu out without shuffling around some of the default applications that ship with Ubuntu. This time around the big news is Evolution, which has been been dethroned as the default mail client and replaced with Mozilla's Thunderbird mail app.

Thunderbird works just fine as an Evolution replacement provided you only used Evolution for email. In fact Thunderbird is in many ways much nicer than Evolution, but there's no denying that it's missing a calendar. You can install Lightning, a calendar plugin for Thunderbird, but considering the migration effort for long-time Evolution users it's probably just easier to skip Thunderbird and simply install Evolution.

Ubuntu 11.10 also sheds a few other things from its past, more notably GNOME 2.x. In the previous release if you didn't like Unity or GNOME 3 you could always revert to the GNOME 2.x look. It wasn't perfect since a few things had already been replaced by GNOME 3 components, but it did, by and large, work.

Those days are over. The option to revert to the GNOME 2.x desktop is now gone. Since 11.10 completes the under the hood upgrade to GNOME 3.0, there is no GNOME 2.x to revert to anymore. As we said in our review of the beta, Unity is here and Canonical's stance is that you're either going to love it or leave it.

If you hate Unity, but want to stick with Ubuntu you can of course use GNOME 3 instead. You'll need to install a few packages, but setting up GNOME 3 for Ubuntu isn't too difficult. If all else fails you can always jump ship to the XFCE desktop, which now counts Linus himself as user.

The truth is Ubuntu 11.10 is a huge improvement over 11.04. Unity is much improved and the often downright terrible performance issues in 11.04 have dramatically improved. If you're okay with Unity then by all means upgrade. If, on the other hand, you're more cautious and want to give Unity more time before you abandon good old GNOME 2 and Ubuntu 10.10, well, there's no reason to rush. Those sticking with Ubuntu 10.10 still have six more months of support, which means six more months for Canonical to improve Unity. Unless you have some clear need to upgrade we suggest riding it out for now.