I used and reviewed OS4 13 (LTS version) earlier, but, I didn't find it appealing. With a change in design, interesting applications pre-installed in the distro and a more refined interface, OS4 13.6 OpenLinux suddenly seems more attractive.
OS4 13 series is based on Xubuntu 12.04 long term release and has Linux kernel 3.2.0. It comes with XFCE 4.10 and Thunar 1.6.3 as the file manager. More or less, it is similar to the offerings made by Xubuntu 12.04 or it's spins in terms of XFCE and Linux kernel. The OS4 release note states of some new additional features as well as introduction of OS4 based desktops and laptops with Acer:
rest here