Disclaimer: I'm a civilian. I just use Linux on a couple of laptops. Arch is a rolling distro with fairly recent applications. Updates most days. Applications

Disclaimer: I'm a civilian. I just use Linux on a couple of laptops. Arch is a rolling distro with fairly recent applications. Updates most days. Applications and system files stay in testing for a period then get pushed out. Very occasional breakage. Installer is bare-bones and uses linux commands a lot. Ubuntu is a 'staged' distro as you well know. I imagine you were using Long Term Support versions of Ubuntu on your servers (10.04, 12.04, 14.04 and so on). The same applies to desktops so 14.04 has pretty stable packages. Ubuntu have announced application upgrades within the LTS period recently. The intermediate releases are supported for 9 months and will therefore have applications nearer to the most recent stable. Not too many updates once you get out of the immediate release period. You might want to have a look at Debian. Unstable is not as quick as Arch with updated applications &c but pretty close. Stable is pretty stable for a couple of years at a time. Repository is huge.