I've setup many VPNs in a variety of environments using OpenVPN over the past year. Most of the VPNs provide tunnels between heterogeneous operating systems and are used 24/7. Thus far, I have not encountered a single unstable installation. Compared to the IPSec firewalls that I have installed in the past, the OpenVPN installations are intuitive, require a fraction of the time, and function properly the first time that they are brought online. I highly recommend OpenVPN over ANY other product that I have used or considered to date.