Evolution remains the mail and calendar client, and with its relatively robust Exchange Server support that's no bad thing.
Karmic Koala takes yet another stab at easing the thorny topic of Linux software installation and management. Out goes the Add/Remove Software tool, in comes the Ubuntu Software Centre. The main interface is separated into sensible categories, but still leaves the user to separate the wheat from the chaff, with no ratings or indication of which applications are popular. It's easier to use than Synaptics Package Manager though (which is still included).
Cloud storage
No longer is it just the software that's free. With the release of Karmic Koala you get free cloud storage too, via the Ubuntu One service. This offers 2GB of free storage, or a flat $10 per month to upgrade to 50GB. Capacity beyond 50GB isn't currently available.
Technical improvements
The biggest noticeable performance boost comes in the shape of faster perceived boot times. The integration of the Upstart process, replacing the age-old init daemon, is the main reason for the quicker feel. Upstart is a multitasking system, allowing startup processes to do their thing in parallel. The init daemon, by contrast, is synchronous, blocking start-up tasks until the previous has completed. Upstart gives faster apparent boot time to the desktop - even if the system hasn't fully finished booting, it feels quick.
The Uncomplicated Firewall (ufw), the front-end for the dauntingly complex iptables firewall tool, gets an update including support for outgoing filtering. It remains a command-line application though, albeit one with (relatively) simple syntax.
