I have used this solution for five years (2008-2013) as the company's main business solution, and then, for a year (2017), as a custom solution for secure AWS access.
I was using it on AWS to create secure access to internal VPC services. It is a lightweight, easy to setup solution.
Several years ago, I was working on a Consumer VPN service provider, and OpenVPN was a great base to provide such services. It is much easier to scale and troubleshoot compared to regular Windows-based VPN solutions or PPTP daemon.
At the moment, I am not working too closely with the product.
More than five years.
On a scale of one to 10, I would rate technical support as a nine.
Just regular Windows Server PPTP/L2TP and Linux PPTP. OpenVPN is clearly better than the regular solutions.
50/50 (straightforward/complex). It requires some experience of Linux server configuration. If you are an experienced Linux user, setup is pretty fast and simple.