This time we're seeing the release of Ubuntu 13.10 which initially wasn't going to have Mir, then was going to in preparation for the next Ubuntu LTS release, but in the end isn't getting it after all. Ubuntu Touch will be using Mir, of course. It's just the desktop flavor that's still on X11.
As with Ubuntu 13.04, Ubuntu 13.10 will have just 9 months of support from release. This reduces the number of parallel versions of Ubuntu that needs to be supported, thus freeing up developer resources to further improve Ubuntu in future releases. How effective this measure will be only time will tell.
The most apparent change in the installer would be the integration of the Ubuntu One cloud storage service.
|Register a new account, or login to your existing Ubuntu One account|
You can create a new Ubuntu One account, or even just login to an existing account during the install process so that Ubuntu One is all ready to go the first time you boot into your freshly installed Ubuntu desktop.
Upgrading from Ubuntu 13.04
The simplest way to start using Ubuntu 13.10 would be to upgrade your existing Ubuntu 13.04 setup. This way all installed software and settings would be retained. It's not the fastest way to get up and running though. If you've installed a lot of software that weren't part of the default install then there's going to be a lot of downloading to do.
Also, anything installed from PPAs will not be upgraded unless those packages happen to be available from the default package repositories. This means software like Handbrake will not be available for a while until after Ubuntu 13.10 is officially out and the maintainers make Saucy packages available from the PPA.
If you happen to use proprietary graphics drivers (for AMD or nVidia GPUs) then you might want to switch back to the open source drivers for the upgrade. I got a borked system after upgrading without first removing Catalyst. Just because it worked fine upgrading from 12.10 to 13.04 with fglrx installed doesn't mean things will work again. That's open source for you, unfortunately.
Even upgrading from the LiveCD environment may not work out. I tried that too with the Final Beta and the upgrade went perfectly. Too bad my USB keyboard and mouse didn't work at all and I had to do a clean installation of 13.04 to get back to a working state.
The official 13.10 release may have fixed it but since the Final Beta is now equivalent to a Release Candidate chances are some users will have similar problems. Just something to keep in mind and prepare for before diving into the new Ubuntu.
Good luck. I'll enjoy my Ubuntu 13.04 for a little while longer...