Going way OT:
The last time I experimented with L2TP on a Windows machine, it required me to modify a registry key for it to work properly. Not impressed...
I've never had that, but even if I had, a registry key is easy. I can write a GPO in just a few minutes and have every laptop in the enterprise use it with a connection profile sent to it. Similarly, I can push L2TP or IPsec policies via MDM. A registry key is really the least of my worries.
I'm honestly more interested in things like DirectAccess than OpenVPN, because it doesn't add management overhead. I'm already managing scores of Windows servers being patched in an automated fashion every month, a couple more is negligible. And I don't need to come up with a method of auditing access and compromised account detection, because with a properly Windows integrated solution (e.g. AnyConnect, DirectAccess, et cetera) I already have auditing systems in place.
But solutions like OpenVPN have their place, where in a more cost sensitive and less security conscious institution without external security auditors, and where the IT staff is small and lacking in the expertise to handle more complex infrastructures, one could easily use it on a small physical server in lieu of a Cisco ASR. I'd say run it virtual, but honestly to make it work properly you need so much virtual overhead with SDN and such that you're better off just getting a physical box and running it as a concentrator on a stick, or going to a more robust virtual solution.
IPSEC ain't any better. Look at the CVEs for Strongswan, for example:
https://www.cvedetails.com/vulnerability-list/vendor_id-2278/Strongswan.html
OpenVPN recently came through two separate security audit. I'd say 2.4.4 is a good point in time for an OpenVPN appliance. A lot of the recent OpenVPN fixes were also related to less frequently used features (like the recent security fix for key method 1, which has been deprecated for years anyway).
The attack vector can be greatly reduced by limiting what OpenVPN features you expose to end-users.
Yes, compared to another VPN product that's also open source and has the same complexity issues, I'd expect the same troubles. I don't expect the same on IOS, CatOS, Junos, or even things like VxWorks. Open source projects seeking to answer every solution introduce additional complexities that are simply unnecessary, and aren't subject to the same QC that most commercial products are with their much more limited scope. Even Windows DA systems are generally more secure, and as I mentioned above, at least they're patched regularly and aren't something more to manage.