Well, I finally got my Raspberry Pi 2 and just could not hold back and wanted to test Snappy Ubuntu Core and give a little introduction and how that thing works.

Ok, but short into: What is Snappy Ubuntu Core?
Well it is meant to be a secure operating system for embedded applications.
It is based on an transactional system-management and can even rollback upgrades of the system core.
There are three kinds of Snappy Ubuntu Core Components:
Snappy Ubuntu Core itself (Core), Frameworks and Apps.
Frameworks can access the Core in certain ways and thus need to be reviewed by the Ubuntu Team.
Apps are completly isolated from each other and have limited access to the system, therefore they don't need special security profiles or reviews, which makes publishing easier.
Ok, and everything is controlled via the command "snappy".

Let's install Snappy Ubuntu Core:
1.) Get the Image from http://www.raspberrypi.org/downloads/ and a Raspberry Pi 2. It needs the ARMv7 architecture and won't run on a RPi 1.
2.) Use the SD Formatter ( https://www.sdcard.org/downloads/formatter_4/ ) with Size Adjustment (you'll find it under Options) ON to format your Micro SD Card and the latest Win32 Disk Imager ( http://sourceforge.net/projects/win32diskimager/ ) to burn the Image to that Micro SD Card.
3.) Plug your RPi 2 into your Keyboard / Monitor / Network Connection, insert the Micro SD Card and let it boot.
4.) The Login Credentials are ubuntu / ubuntu

Ok. Now that we got Snappy Ubuntu Core running on our RPi 2 - how about using it?
We can login via Keyboard / Monitor using the CLI, or use SSH - if we know the IP Address of our RPi2.
Login Credentials remain the same.
Additionally, we can browser from any PC on the same network to http://:4200/ - which is the unsecured (NO LOGIN!) web device manager called WebDM. We can use it to install new Apps and work on the RPi 2. But as said, it has no authentication in this version - so... Don't use this box for anything more than testing / dev work!

After login in, we can find out the most important things via uname -a, top, df -h, date and ifconfig.

Snappy Ubuntu Core uses about 128 MB of RAM while beeing idle.

The most important thing is to activate the NTP Client on your Box. Otherwise the RTC will start at somewhere around 1970 and your system won't be able to update anything, as the certificates on your device will be invalid. So enable that via the command sudo timedatectl set-ntp true. You could also set the time manually via i.e. sudo date -s "Tue 2 Mar 21:33 UTC 2015".

After that is done, we can watch or current installed apps, frameworks and system via snappy info. An exact view on our system with version numbers and which part is active (due to the transactional style we can have multiple versions installed and even switch back to the older version if something fails on the upgrade) can be seen via sudo snappy versions -a. To get the latest version information (i.e. like sudo apt-get update), we use the command sudo snappy update-versions and watch the new versions via sudo snappy versions -a. We can finally upgrade the system via sudo snappy update ubuntu-core for i.e. updating the core. After an sudo reboot, the latest version will come up and also be shown on the sudo snappy versions -a screen.

Little Hint: On my last test, Snappy showed this output:
ubuntu@localhost:~$ sudo snappy versions -a
Part Tag Installed Available Fingerprint Active
ubuntu-core edge 2 3 f442b1d8d6db3f *
ubuntu-core edge 3 - d3fe721a35104a R
webdm edge 0.1 - 1604c8b7c9f6c5 *
Run 'snappy update' and reboot to use the new ubuntu-core.

Which means the new Version should come up on Reboot ("Active, R") - however, even after rebooting several times and other trys - I could not get it to work and change to Version 3 of the Ubuntu Core :/!

Last but not least: How to find and install new apps? Very easy.
Just enter i.e. snappy search to find the App you're looking for and install it with sudo snappy install or via the WebDM System.

More infos can be found on the Website of Snappy Ubuntu Core: https://developer.ubuntu.com/en/snappy/

PS: As already added, this release is still in its beta stages and is not really "snappy" in terms of speed compared to an Raspbian or similiar Image. Also there are not a lot of Apps to choose from and there are several security problems like the complete open WebDM. Be advised that Snappy Ubuntu Core is NOT YET READY FOR PRODUCTION USE.