[Chris83]

I also couldn't update because of the dependency issue mentioned above.
Apparently there is no libc6 >=2.14 for ARM processors and I think the current package list is not looking for an ARM compatible libsystemd-login0. So I thought I update the files at least to the latest available level and see if I can avoid the issues people reported if you do not update them at all.
1. I first made a full backup.
2. I then manually installed the latest libc6 for ARM I could find:
wget https://archive.raspbian.org/raspbian/pool/main/e/eglibc/libc6_2.13-38+rpi2+deb7u3_armhf.deb
dpkg -i --force-all libc6_2.13-38+rpi2+deb7u3_armhf.deb
apt-get -f install
3. I manually installed the latest libsystemd-login0 for ARM I could find:
wget http://ftp.de.debian.org/debian/pool/main/s/systemd/libsystemd-login0_44-11+deb7u4_armhf.deb
dpkg -i --force-all libsystemd-login0_44-11+deb7u4_armhf.deb
apt-get -f install
4. Then I updated everything else (except libsystemd-login0, which still complains) via xbian-config.
5. Restarted and no issues so far. XBMC, Airplay, Transmission, Flexget, Samba and SSH is working.