Current strengths
OpenVPN 2.3 is light years ahead of where we stood in the recent past. A quick glance at the change list from around 2008 until now shows quite a significant number of important updates, bug fixes, and enhancements.
There are a number of things OpenVPN does well. OpenVPN is extensible, pluggable, and dynamic. It has functional support for IPv6, push default gateway (even in broken networks), and floating across public IPs while maintaining connections.
Cross-platform support is unbeatable across the various VPN implementations.